WorldWideScience

Sample records for nest predation rates

  1. Do Predation Rates on Artificial Nests Accurately Reflect Predation Rates on Natural Bird Nests?

    Science.gov (United States)

    David I. King; Richard M. DeGraaf; Curtice R. Griffin; Thomas J. Maier

    1999-01-01

    Artificial nests are widely used in avian field studies. However, it is unclear how well predation rates on artificial nests reflect predation rates on natural nests. Therefore, we compared survival rates of artificial nests (unused natural nests baited with House Sparrow eggs) with survival rates of active bird nests in the same habitat at the same sites. Survival...

  2. Predators and predation rates of skylark Alauda arvensis and woodlark Lullula arborea nests in a semi-natural area in the Netherlands

    NARCIS (Netherlands)

    Praus, Libor; Hegemann, Arne; Tieleman, B. Irene; Weidinger, Karel

    2014-01-01

    Predation is a major cause of breeding failure in bird species with open nests. Although many studies have investigated nest predation rates, direct identification of nest predators is sporadic, especially in (semi-)natural habitats. We quantified nest success and identified nest predators in a

  3. Landscape forest cover and edge effects on songbird nest predation vary by nest predator

    Science.gov (United States)

    W. Andrew Cox; Frank R. III Thompson; John. Faaborg

    2012-01-01

    Rates of nest predation for birds vary between and within species across multiple spatial scales, but we have a poor understanding of which predators drive such patterns. We video-monitored nests and identified predators at 120 nests of the Acadian Flycatcher (Empidonax virescens) and the Indigo Bunting (Passerina cyanea) at eight...

  4. Differences in predators of artificial and real songbirds nests: Evidence of bias in artificial nest studies

    Science.gov (United States)

    Frank R. Thompson; Dirk E. Burhans

    2004-01-01

    In the past two decades, many researchers have used artificial nest to measure relative rates of nest predation. Recent comparisons show that real and artificial nests may not be depredated at the same rate, but no one has examined the mechanisms underlying these patterns. We determined differences in predator-specific predation rates of real and artificial nests. we...

  5. Predation risk of artificial ground nests in managed floodplain meadows

    Science.gov (United States)

    Arbeiter, Susanne; Franke, Elisabeth

    2018-01-01

    Nest predation highly determines the reproductive success in birds. In agricultural grasslands, vegetation characteristics and management practices influences the predation risk of ground breeders. Little is known so far on the predation pressure on non-passerine nests in tall swards. Investigations on the interaction of land use with nesting site conditions and the habitat selection of nest predators are crucial to develop effective conservation measures for grassland birds. In this study, we used artificial nests baited with quail and plasticine eggs to identify potential predators of ground nests in floodplain meadows and related predation risk to vegetation structure and grassland management. Mean daily predation rate was 0.01 (±0.012) after an exposure duration of 21 days. 70% of all observed nest predations were caused by mammals (Red Fox and mustelids) and 17.5% by avian predators (corvids). Nest sites close to the meadow edge and those providing low forb cover were faced with a higher daily predation risk. Predation risk also increased later in the season. Land use in the preceding year had a significant effect on predation risk, showing higher predation rates on unmanaged sites than on mown sites. Unused meadows probably attract mammalian predators, because they provide a high abundance of small rodents and a more favourable vegetation structure for foraging, increasing also the risk of incidental nest predations. Although mowing operation is a major threat to ground-nesting birds, our results suggest that an annual removal of vegetation may reduce predation risk in the subsequent year.

  6. Enclosed nests may provide greater thermal than nest predation benefits compared with open nests across latitudes

    Science.gov (United States)

    Martin, Thomas E.; Boyce, Andy J.; Fierro-Calderon, Karolina; Mitchell, Adam E.; Armstad, Connor E.; Mouton, James C.; Bin Soudi, Evertius E.

    2017-01-01

    Nest structure is thought to provide benefits that have fitness consequences for several taxa. Traditionally, reduced nest predation has been considered the primary benefit underlying evolution of nest structure, whereas thermal benefits have been considered a secondary or even non-existent factor. Yet, the relative roles of these factors on nest structures remain largely unexplored.Enclosed nests have a constructed or natural roof connected to sides that allow a restricted opening or tube entrance that provides cover in all directions except the entrance, whereas open nests are cups or platforms that are open above. We show that construction of enclosed nests is more common among songbirds (Passeriformes) in tropical and southern hemisphere regions than in north temperate regions. This geographic pattern may reflect selection from predation risk, under long-standing assumptions that nest predation rates are higher in southern regions and that enclosed nests reduce predation risk compared with open cup nests. We therefore compared nest predation rates between enclosed vs. open nests in 114 songbird species that do not nest in tree holes among five communities of coexisting birds, and for 205 non-hole-nesting species from the literature, across northern temperate, tropical, and southern hemisphere regions.Among coexisting species, enclosed nests had lower nest predation rates than open nests in two south temperate sites, but not in either of two tropical sites or a north temperate site. Nest predation did not differ between nest types at any latitude based on literature data. Among 319 species from both our field studies and the literature, enclosed nests did not show consistent benefits of reduced predation and, in fact, predation was not consistently higher in the tropics, contrary to long-standing perspectives.Thermal benefits of enclosed nests were indicated based on three indirect results. First, species that built enclosed nests were smaller than species using

  7. Parental investment decisions in response to ambient nest-predation risk versus actual predation on the prior nest

    Science.gov (United States)

    Chalfoun, A.D.; Martin, T.E.

    2010-01-01

    Theory predicts that parents should invest less in dependent offspring with lower reproductive value, such as those with a high risk of predation. Moreover, high predation risk can favor reduced parental activity when such activity attracts nest predators. Yet, the ability of parents to assess ambient nest-predation risk and respond adaptively remains unclear, especially where nest-predator assemblages are diverse and potentially difficult to assess. We tested whether variation in parental investment by a multi-brooded songbird (Brewer's Sparrow, Spizella breweri) in an environment (sagebrush steppe) with diverse predators was predicted by ambient nest-predation risk or direct experience with nest predation. Variation among eight sites in ambient nest-predation risk, assayed by daily probabilities of nest predation, was largely uncorrelated across four years. In this system risk may therefore be unpredictable, and aspects of parental investment (clutch size, egg mass, incubation rhythms, nestling-feeding rates) were not related to ambient risk. Moreover, investment at first nests that were successful did not differ from that at nests that were depredated, suggesting parents could not assess and respond to territorylevel nest-predation risk. However, parents whose nests were depredated reduced clutch sizes and activity at nests attempted later in the season by increasing the length of incubation shifts (on-bouts) and recesses (off-bouts) and decreasing trips to feed nestlings. In this unpredictable environment parent birds may therefore lack sufficient cues of ambient risk on which to base their investment decisions and instead rely on direct experience with nest predation to inform at least some of their decisions. ?? 2010 The Cooper Ornithological Society.

  8. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird.

    Science.gov (United States)

    Hollander, Franck A; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

  9. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird.

    Directory of Open Access Journals (Sweden)

    Franck A Hollander

    Full Text Available In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

  10. How avian nest site selection responds to predation risk: Testing an 'adaptive peak hypothesis'

    Science.gov (United States)

    Quresh S. Latif; Sacha K. Heath; John T. Rotenberry

    2012-01-01

    1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates. 2. This lack of congruence between theory-based expectation and empirical data may arise when birds already occupy ‘adaptive peaks’. If birds nest...

  11. Response of predators to Western Sandpiper nest exclosures

    Science.gov (United States)

    Niehaus, Amanda C.; Ruthrauff, Daniel R.; McCaffery, Brian J.

    2004-01-01

    In 2001, predator exclosures were used to protect nests of the Western Sandpiper (Calidris mauri) in western Alaska. During the exclosure experiment, nest contents in exclosures had significantly higher daily survival rates than control nests, however, late in the study predators began to cue in on exclosures and predate the nest contents. An Arctic Fox (Alopex lagopus) dug under one exclosure and took the newly hatched chicks, and Long-tailed Jaegers (Stercorarius longicaudus) learned to associate exclosures with active nests and repeatedly visited them. The jaegers attempted to gain access to exclosed nests and pursued adult sandpipers as they emerged from the exclosures. The exclosures were removed to reduce potential mortality to adult and young sandpipers, but subsequently, post-exclosure nests had lower daily survival rates than controls during the same time period. Predation of post-exclosure eggs and chicks highlighted the lasting influence of the exclosure treatment on offspring survival because predators probably remembered nest locations. Researchers are urged to use caution when considering use of predator exclosures in areas where jaegers occur.

  12. Nest Predation Deviates from Nest Predator Abundance in an Ecologically Trapped Bird

    OpenAIRE

    Hollander, Franck A.; Van Dyck, Hans; San Martin, Gilles; Titeux, Nicolas

    2015-01-01

    In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius ...

  13. Using Artificial Nests to Study Nest Predation in Birds

    Science.gov (United States)

    Belthoff, James R.

    2005-01-01

    A simple and effective field exercise that demonstrates factors affecting predation on bird nests is described. With instructor guidance, students in high school biology or college-level biology, ecology, animal behavior, wildlife management or ornithology laboratory courses can collaborate to design field experiments related to nest depredation.

  14. Effects of parents and Brown-headed Cowbirds (Molothrus ater) on nest predation risk for a songbird

    Science.gov (United States)

    Quresh S. Latif; Sacha K. Heath; John T. Rotenberry

    2012-01-01

    Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for songbirds. Previous...

  15. Nest predation risk explains variation in avian clutch size

    Science.gov (United States)

    Dillon, Kristen G.; Conway, Courtney J.

    2018-01-01

    Questions about the ecological drivers of, and mechanistic constraints on, productivity have driven research on life-history evolution for decades. Resource availability and offspring mortality are considered among the 2 most important influences on the number of offspring per reproductive attempt. We used a factorial experimental design to manipulate food abundance and perceived offspring predation risk in a wild avian population (red-faced warblers; Cardellina rubrifrons) to identify the mechanistic cause of variation in avian clutch size. Additionally, we tested whether female quality helped explain the extant variation in clutch size. We found no support for the Food Limitation or Female Quality Hypotheses, but we did find support for both predictions of the Nest Predation Risk Hypothesis. Females that experienced an experimentally heightened perception of offspring predation risk responded by laying a smaller clutch than females in the control group. Additionally, predation rates at artificial nests were highest where red-faced warbler clutch size was smallest (at high elevations). Life-history theory predicts that an individual should invest less in reproduction when high nest predation risk reduces the likely benefit from that nesting attempt and, indeed, we found that birds exhibit phenotypic plasticity in clutch size by laying fewer eggs in response to increasing nest predation risk.

  16. Informed renesting decisions: the effect of nest predation risk.

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    Pakanen, Veli-Matti; Rönkä, Nelli; Thomson, Robert L; Koivula, Kari

    2014-04-01

    Animals should cue on information that predicts reproductive success. After failure of an initial reproductive attempt, decisions on whether or not to initiate a second reproductive attempt may be affected by individual experience and social information. If the prospects of breeding success are poor, long-lived animals in particular should not invest in current reproductive success (CRS) in case it generates costs to future reproductive success (FRS). In birds, predation risk experienced during breeding may provide a cue for renesting success. Species having a high FRS potential should be flexible and take predation risk into account in their renesting decisions. We tested this prediction using breeding data of a long-lived wader, the southern dunlin Calidris alpina schinzii. As predicted, dunlin cued on predation risk information acquired from direct experience of nest failure due to predation and ambient nest predation risk. While the overall renesting rate was low (34.5%), the early season renesting rate was high but declined with season, indicating probable temporal changes in the costs and benefits of renesting. We develop a conceptual cost-benefit model to describe the effects of the phase and the length of breeding season on predation risk responses in renesting. We suggest that species investing in FRS should not continue breeding in short breeding seasons in response to predation risk but without time constraints, their response should be similar to species investing in CRS, e.g. within-season dispersal and increased nest concealment.

  17. Determining nest predators of the Least Bell's Vireo through point counts, tracking stations, and video photography

    Science.gov (United States)

    Peterson, Bonnie L.; Kus, Barbara E.; Deutschman, Douglas H.

    2004-01-01

    We compared three methods to determine nest predators of the Least Bell's Vireo (Vireo bellii pusillus) in San Diego County, California, during spring and summer 2000. Point counts and tracking stations were used to identify potential predators and video photography to document actual nest predators. Parental behavior at depredated nests was compared to that at successful nests to determine whether activity (frequency of trips to and from the nest) and singing vs. non-singing on the nest affected nest predation. Yellow-breasted Chats (Icteria virens) were the most abundant potential avian predator, followed by Western Scrub-Jays (Aphelocoma californica). Coyotes (Canis latrans) were abundant, with smaller mammalian predators occurring in low abundance. Cameras documented a 48% predation rate with scrub-jays as the major nest predators (67%), but Virginia opossums (Didelphis virginiana, 17%), gopher snakes (Pituophis melanoleucus, 8%) and Argentine ants (Linepithema humile, 8%) were also confirmed predators. Identification of potential predators from tracking stations and point counts demonstrated only moderate correspondence with actual nest predators. Parental behavior at the nest prior to depredation was not related to nest outcome.

  18. Effects of parents and Brown-headed Cowbirds (Molothrus ater) on nest predation risk for a songbird

    Science.gov (United States)

    Latif, Quresh S; Heath, Sacha K; Rotenberry, John T

    2012-01-01

    Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for songbirds. Previous work reproduced microhabitat-predation patterns experienced by Yellow Warblers (Setophaga petechia) in the Mono Lake basin at experimental nests without parents, suggesting that these patterns were driven by predator ecology rather than predator interactions with parents. In this study, we further explored effects of post-initiation parental behavior (nest defense and attendance) on predation risk by comparing natural versus experimental patterns related to territory density, seasonal timing of nest initiation, and nest age. Rates of parasitism by Brown-headed Cowbirds (Molothrus ater) were high in this system (49% nests parasitized), so we also examined parasitism-predation relationships. Natural nest predation rates (NPR) correlated negatively with breeding territory density and nonlinearly (U-shaped relationship) with nest-initiation timing, but experimental nests recorded no such patterns. After adjusting natural-nest data to control for these differences from experimental nests other than the presence of parents (e.g., defining nest failure similarly and excluding nestling-period data), we obtained similar results. Thus, parents were necessary to produce observed patterns. Lower natural NPR compared with experimental NPR suggested that parents reduced predation rates via nest defense, so this parental behavior or its consequences were likely correlated with density or seasonal timing. In contrast, daily predation rates decreased with nest age for both nest types, indicating this pattern did not involve parents. Parasitized nests suffered higher rates of partial predation but lower rates of

  19. Temporal variation in black-caiman-nest predation in varzea of central Brazilian amazonia.

    Science.gov (United States)

    Torralvo, Kelly; Botero-Arias, Robinson; Magnusson, William E

    2017-01-01

    On the Amazon floodplain, the main predators of black caiman (Melanosuchus niger) eggs are jaguars (Panthera onca), tegu lizards (Tupinambis teguixim), capuchin monkeys (Sapajus macrocephalus) and humans (Homo sapiens). In this study, we investigated the relationship between predator attacks on nests and incubation period, and evaluated the influence of initial predation on subsequent predation in the Mamirauá Sustainable Development Reserve. We also evaluated the influence of presence of females near the nests and manipulation of nests on the occurrence of attacks. We compared results from data obtained with camera traps and vestiges left by predators on estimates of rates of predation by different predators. Egg predation was recorded in 32% of the 658 black caiman nests monitored during two years. Our results suggest that the probability of predation on black caiman eggs is relatively constant throughout the incubation period and that predation on eggs was lower when adults, presumably females, were present. Careful opening of nests and handling of eggs did not increase the number of attacks on black caiman nests. Nest opening by a predator appeared to increase the chances of a subsequent attack because most of the attacks on nests occurred soon after a predator first opened the nest. However, attacks by another species of predator do not appear to be necessary to initiate attacks by any other species of predator. Results based on camera traps and vestiges differed, but use of vestiges was adequate for identifying the principal predators on eggs in black caiman nests and, in many circumstances, the vestiges may be better for estimating predation by humans. In this study, opening nests and handling eggs did not increase the number of attacks on black caiman nests.

  20. Temporal variation in black-caiman-nest predation in varzea of central Brazilian amazonia.

    Directory of Open Access Journals (Sweden)

    Kelly Torralvo

    Full Text Available On the Amazon floodplain, the main predators of black caiman (Melanosuchus niger eggs are jaguars (Panthera onca, tegu lizards (Tupinambis teguixim, capuchin monkeys (Sapajus macrocephalus and humans (Homo sapiens. In this study, we investigated the relationship between predator attacks on nests and incubation period, and evaluated the influence of initial predation on subsequent predation in the Mamirauá Sustainable Development Reserve. We also evaluated the influence of presence of females near the nests and manipulation of nests on the occurrence of attacks. We compared results from data obtained with camera traps and vestiges left by predators on estimates of rates of predation by different predators. Egg predation was recorded in 32% of the 658 black caiman nests monitored during two years. Our results suggest that the probability of predation on black caiman eggs is relatively constant throughout the incubation period and that predation on eggs was lower when adults, presumably females, were present. Careful opening of nests and handling of eggs did not increase the number of attacks on black caiman nests. Nest opening by a predator appeared to increase the chances of a subsequent attack because most of the attacks on nests occurred soon after a predator first opened the nest. However, attacks by another species of predator do not appear to be necessary to initiate attacks by any other species of predator. Results based on camera traps and vestiges differed, but use of vestiges was adequate for identifying the principal predators on eggs in black caiman nests and, in many circumstances, the vestiges may be better for estimating predation by humans. In this study, opening nests and handling eggs did not increase the number of attacks on black caiman nests.

  1. Nest predators of open and cavity nesting birds in oak woodlands

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    Kathryn L. Purcell; Jared Verner

    1999-01-01

    Camera setups revealed at least three species of rodents and seven species of birds as potential predators at artificial open nests. Surprisingly, among avian predators identified at open nests, one third were Bullock's Orioles (Icterus bullockii). Two rodent species and three bird species were potential predators at artificial cavity nests. This high predator...

  2. Avoiding the nest : responses of field sparrows to the threat of nest predation

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    Dirk E. Burhans

    2000-01-01

    Nest predation is a major source of reproductive failure in birds (Ricklefs 1969, Martin 1992). Birds confronted with an enemy near the nest may use behaviors to deter the prospect of nest predation. The benefits of nest defense have been shown for many agressive species (Martin 1992), but smaller birds that cannot deter predators may need to resort to other behaviors...

  3. Power lines, roads, and avian nest survival: effects on predator identity and predation intensity.

    Science.gov (United States)

    DeGregorio, Brett A; Weatherhead, Patrick J; Sperry, Jinelle H

    2014-05-01

    1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to

  4. Conservation implications when the nest predators are known

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    Ribic, Christine; Thompson, Frank

    2012-01-01

    Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using video surveillance to identify nest predators allow researchers to start evaluating what methods could be used to mitigate nest predation to help passerines of conservation concern. From recent studies, we identified latitudinal and habitat-related patterns in the importance of predator groups that depredate passerine nests. We then reviewed how knowledge of specific nest predators can benefit conservation of bird species of concern. Mammals were the dominant predator group in northern grasslands. Snakes were the dominant predator group in southern habitats. Fire ants were only a nest predator in southern latitudes. Differences in the importance of predator species or groups were likely the result of both their geographic patterns of distribution and habitat preferences. Some direct and indirect predator control measures developed for waterfowl management potentially could be used to benefit passerine productivity. We reviewed three examples-cowbirds, snakes in shrublands, and ground squirrels in grasslands-to illustrate how different predator control strategies may be needed in different situations. Mitigation of passerine nest predation will need to be based on knowledge of predator communities to be effective. This requires large samples of predation events with identified predators; video technology is essential for this task.

  5. Generalist predator, cyclic voles and cavity nests: testing the alternative prey hypothesis.

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    Pöysä, Hannu; Jalava, Kaisa; Paasivaara, Antti

    2016-12-01

    The alternative prey hypothesis (APH) states that when the density of the main prey declines, generalist predators switch to alternative prey and vice versa, meaning that predation pressure on the alternative prey should be negatively correlated with the density of the main prey. We tested the APH in a system comprising one generalist predator (pine marten, Martes martes), cyclic main prey (microtine voles, Microtus agrestis and Myodes glareolus) and alternative prey (cavity nests of common goldeneye, Bucephala clangula); pine marten is an important predator of both voles and common goldeneye nests. Specifically, we studied whether annual predation rate of real common goldeneye nests and experimental nests is negatively associated with fluctuation in the density of voles in four study areas in southern Finland in 2000-2011. Both vole density and nest predation rate varied considerably between years in all study areas. However, we did not find support for the hypothesis that vole dynamics indirectly affects predation rate of cavity nests in the way predicted by the APH. On the contrary, the probability of predation increased with vole spring abundance for both real and experimental nests. Furthermore, a crash in vole abundance from previous autumn to spring did not increase the probability of predation of real nests, although it increased that of experimental nests. We suggest that learned predation by pine marten individuals, coupled with efficient search image for cavities, overrides possible indirect positive effects of high vole density on the alternative prey in our study system.

  6. Variability in nest survival rates and implications to nesting studies

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    Klett, A.T.; Johnson, D.H.

    1982-01-01

    We used four reasonably large samples (83-213) of Mallard (Anas platyrhynchos) and Blue-winged Teal (A. discors) nests on an interstate highway right-of-way in southcentral North Dakota to evaluate potential biases in hatch-rate estimates. Twelve consecutive, weekly searches for nests were conducted with a cable-chain drag in 1976 and 1977. Nests were revisited at weekly intervals. Four methods were used to estimate hatch rates for the four data sets: the Traditional Method, the Mayfield Method, and two modifications of the Mayfield Method that are sometimes appropriate when daily mortality rates of nests are not constant. Hatch rates and the average age of nests at discovery declined as the interval between searches decreased, suggesting that mortality rates were not constant in our samples. An analysis of variance indicated that daily mortality rates varied with the age of nests in all four samples. Mortality was generally highest during the early laying period, moderately high during the late laying period, and lowest during incubation. We speculate that this relationship of mortality to nest age might be due to the presence of hens at nests or to differences in the vulnerability of nest sites to predation. A modification of the Mayfield Method that accounts for age-related variation in nest mortality was most appropriate for our samples. We suggest methods for conducting nesting studies and estimating nest success for species possessing similar nesting habits.

  7. Anti-predator meshing may provide greater protection for sea turtle nests than predator removal.

    Directory of Open Access Journals (Sweden)

    Julie M O'Connor

    Full Text Available The problem of how to protect sea turtle nests from terrestrial predators is of worldwide concern. On Queensland's southern Sunshine Coast, depredation of turtle nests by the introduced European red fox (Vulpes vulpes has been recorded as the primary terrestrial cause of egg and hatchling mortality. We investigated the impact of foxes on the nests of the loggerhead turtle (Caretta caretta and occasional green turtle (Chelonia mydas over ten nesting seasons. Meshing of nests with fox exclusion devices (FEDs was undertaken in all years accompanied by lethal fox control in the first five-year period, but not in the second five-year period. Lethal fox control was undertaken in the study area from 2005 to February 2010, but foxes still breached 27% (range19-52% of turtle nests. In the second five-year period, despite the absence of lethal fox control, the average percentage of nests breached was less than 3% (range 0-4%. Comparison of clutch depredation rates in the two five-year periods demonstrated that continuous nest meshing may be more effective than lethal fox control in mitigating the impact of foxes on turtle nests. In the absence of unlimited resources available for the eradication of exotic predators, the use of FEDs and the support and resourcing of a dedicated volunteer base can be considered an effective turtle conservation tool on some beaches.

  8. Anti-predator meshing may provide greater protection for sea turtle nests than predator removal.

    Science.gov (United States)

    O'Connor, Julie M; Limpus, Colin J; Hofmeister, Kate M; Allen, Benjamin L; Burnett, Scott E

    2017-01-01

    The problem of how to protect sea turtle nests from terrestrial predators is of worldwide concern. On Queensland's southern Sunshine Coast, depredation of turtle nests by the introduced European red fox (Vulpes vulpes) has been recorded as the primary terrestrial cause of egg and hatchling mortality. We investigated the impact of foxes on the nests of the loggerhead turtle (Caretta caretta) and occasional green turtle (Chelonia mydas) over ten nesting seasons. Meshing of nests with fox exclusion devices (FEDs) was undertaken in all years accompanied by lethal fox control in the first five-year period, but not in the second five-year period. Lethal fox control was undertaken in the study area from 2005 to February 2010, but foxes still breached 27% (range19-52%) of turtle nests. In the second five-year period, despite the absence of lethal fox control, the average percentage of nests breached was less than 3% (range 0-4%). Comparison of clutch depredation rates in the two five-year periods demonstrated that continuous nest meshing may be more effective than lethal fox control in mitigating the impact of foxes on turtle nests. In the absence of unlimited resources available for the eradication of exotic predators, the use of FEDs and the support and resourcing of a dedicated volunteer base can be considered an effective turtle conservation tool on some beaches.

  9. Female in-nest chatter song increases predation.

    Science.gov (United States)

    Kleindorfer, Sonia; Evans, Christine; Mahr, Katharina

    2016-01-01

    Female song is an ancestral trait in songbirds, yet extant females generally sing less than males. Here, we examine sex differences in the predation cost of singing behaviour. The superb fairy-wren (Malurus cyaneus) is a Southern Hemisphere songbird; males and females provision the brood and produce solo song year-round. Both sexes had higher song rate during the fertile period and lower song rate during incubation and chick feeding. Females were more likely than males to sing close to or inside the nest. For this reason, female but not male song rate predicted egg and nestling predation. This study identifies a high fitness cost of song when a parent bird attends offspring inside a nest and explains gender differences in singing when there are gender differences in parental care. © 2016 The Author(s).

  10. Gregarious nesting - An anti-predator response in laying hens

    DEFF Research Database (Denmark)

    Riber, Anja Brinch

    2012-01-01

    Gregarious nesting can be defined as a behaviour that occurs when a laying hen (Gallus gallus domesticus) given the choice between an occupied and an unoccupied nest site chooses the occupied nest site. It occurs frequently in flocks of laying hens kept under commercial conditions, contrasting...... the behaviour displayed by feral hens that isolate themselves from the flock during nesting activities. What motivates laying hens to perform gregarious nesting is unknown. One possibility is that gregarious nesting is an anti-predator response to the risk of nest predation emerging from behavioural flexibility...

  11. Nest predation research: Recent findings and future perspectives

    Science.gov (United States)

    Chalfoun, Anna D.; Ibanez-Alamo, J. D.; Magrath, R. D.; Schmidt, Kenneth A.; Thomson, R. L.; Oteyza, Juan C.; Haff, T. M.; Martin, T.E.

    2016-01-01

    Nest predation is a key source of selection for birds that has attracted increasing attention from ornithologists. The inclusion of new concepts applicable to nest predation that stem from social information, eavesdropping or physiology has expanded our knowledge considerably. Recent methodological advancements now allow focus on all three players within nest predation interactions: adults, offspring and predators. Indeed, the study of nest predation now forms a vital part of avian research in several fields, including animal behaviour, population ecology, evolution and conservation biology. However, within nest predation research there are important aspects that require further development, such as the comparison between ecological and evolutionary antipredator responses, and the role of anthropogenic change. We hope this review of recent findings and the presentation of new research avenues will encourage researchers to study this important and interesting selective pressure, and ultimately will help us to better understand the biology of birds.

  12. Use of artificial nests to investigate predation on freshwater turtle nests

    Science.gov (United States)

    Michael N. Marchand; John A. Litvaitis; Thomas J. Maier; Richard M. DeGraaf

    2002-01-01

    Habitat fragmentation has raised concerns that populations of generalist predators have increased and are affecting a diverse group of prey. Previous research has included the use of artificial nests to investigate the role of predation on birds that nest on or near the ground. Because predation also is a major factor limiting populations of freshwater turtles, we...

  13. Nest predation increases with parental activity: separating nest site and parental activity effects.

    OpenAIRE

    Martin, T E; Scott, J; Menge, C

    2000-01-01

    Alexander Skutch hypothesized that increased parental activity can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental activity was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental activity between nesting stages across the ten study species. Previous investigators h...

  14. Linking snake habitat use to nest predation risk in grassland birds: the dangers of shrub cover.

    Science.gov (United States)

    Klug, Page E; Jackrel, Sara L; With, Kimberly A

    2010-03-01

    Extremes in rangeland management, varying from too-frequent fire and intensive grazing to the suppression of both, threaten rangeland ecosystems worldwide. Intensive fire and grazing denude and homogenize vegetation whereas their suppression increases woody cover. Although habitat loss is implicated in grassland bird declines, degradation through intensive management or neglect also decreases breeding habitat and may reduce nesting success through increased rates of nest predation. Snakes are important nest predators, but little is known about how habitat use in snakes relates to predation risk for grassland birds nesting within tallgrass prairie subjected to different grazing and fire frequencies. We evaluated nest survival in the context of habitat used by nesting songbirds and two bird-eating snakes, the eastern yellowbelly racer Coluber constrictor flaviventris and Great Plains ratsnake Pantherophis emoryi. Daily nest survival rates decreased with increasing shrub cover and decreasing vegetation height, which characterize grasslands that have been neglected or intensively managed, respectively. Discriminant function analysis revealed that snake habitats were characterized by higher shrub cover, whereas successful nests were more likely to occur in areas with tall grass and forbs but reduced shrub cover. Because snakes often use shrub habitat, birds nesting in areas with increased shrub cover may be at higher risk of nest predation by snakes in addition to other predators known to use shrub habitat (e.g., mid-sized carnivores and avian predators). Depredated nests also occurred outside the discriminant space of the snakes, indicating that other predators (e.g., ground squirrels Spermophilus spp. and bullsnakes Pituophis catenifer) may be important in areas with denuded cover. Targeted removal of shrubs may increase nest success by minimizing the activity of nest predators attracted to shrub cover.

  15. ENSO, nest predation risk, food abundance, and male status fail to explain annual variations in the apparent survival rate of a migratory songbird.

    Directory of Open Access Journals (Sweden)

    Alizée Vernouillet

    Full Text Available Adult mortality can be a major driver of population decline in species whose productivity is relatively low. Yet, little is known about the factors influencing adult survival rates in migratory bird species, nor do we know much about the longer-term effects of habitat disturbance on the fitness of individuals. The Ovenbird (Seiurus aurocapilla is one of the vertebrate species most sensitive to forest management, yet it is still common and widespread. We monitored the fate of 330 colour-banded Ovenbird males in four pairs of 25-ha plots during 9 successive breeding seasons. One plot of each pair was treated through selection harvesting (30-40% basal area removed during the first winter. We tested the following hypotheses: (1 higher physiological costs in harvested plots as a result of lower food abundance will reduce apparent survival rate (ASR relative to controls; (2 lower ASR following years with low nest survival and higher probability of renesting; (3 fluctuations in ASR reflecting El Niño Southern Oscillation (ENSO; and (4 higher ASR in returning males than in recruits (unbanded immigrants owing to greater site familiarity in the former. We tested the relative importance of these hypotheses, or combinations thereof, by generating 23 models explaining variation in ASR. The year-dependent model received the most support, showing a 41% decrease in ASR from 2007 to 2014. The important year-to-year variation we observed in ASR (Σw(i = 0.99 was not explained by variation in nest predation risk nor by ENSO. There was also little evidence for an effect of selection harvesting on ASR of Ovenbird males, despite a slight reduction in lifespan relative to males from control plots (2.7 vs 2.9 years. An avenue worth exploring to explain this intriguing pattern would be to determine whether conditions at migratory stopover sites or in the wintering area of our focal population have gradually worsened over the past decade.

  16. Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA (Presentation)

    Science.gov (United States)

    Many empirical studies have shown that forest-breeding songbirds suffer greater rates of nest predation and nest parasitism in smaller forest patches and in fragmented landscapes. To compare the performance of different metrics of spatial habitat configuration resulting from defo...

  17. Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition.

    Science.gov (United States)

    Fisher, Ryan J; Wiebe, Karen L

    2006-04-01

    To date, most studies of nest site selection have failed to take into account more than one source of nest loss (or have combined all sources in one analysis) when examining nest site characteristics, leaving us with an incomplete understanding of the potential trade-offs that individuals may face when selecting a nest site. Our objectives were to determine whether northern flickers (Colaptes auratus) may experience a trade-off in nest site selection in response to mammalian nest predation and nest loss to a cavity nest competitor (European starling, Sturnus vulgaris). We also document within-season temporal patterns of these two sources of nest loss with the hypothesis that flickers may also be constrained in the timing of reproduction under both predatory and competitive influence. Mammalian predators frequently depredated flicker nests that were: lower to the ground, less concealed by vegetation around the cavity entrance and at the base of the nest tree, closer to coniferous forest edges and in forest clumps with a high percentage of conifer content. Proximity to coniferous edges or coniferous trees increased the probability of nest predation, but nests near conifers were less likely to be lost to starlings. Flickers may thus face a trade-off in nest site selection with respect to safety from predators or competitors. Models suggested that peaks of nest predation and nest loss to eviction occurred at the same time, although a competing model suggested that the peak of nest loss to starlings occurred 5 days earlier than the peak of mammalian predation. Differences in peaks of mammalian predation and loss to starlings may constrain any adjustment in clutch initiation date by flickers to avoid one source of nest loss.

  18. The nest predator assemblage for songbirds in Mono Lake basin riparian habitats

    Science.gov (United States)

    Quresh S. Latif; Sacha K. Heath; Grant Ballard

    2012-01-01

    Because nest predation strongly limits avian fitness, ornithologists identify nest predators to inform ecological research and conservation. During 2002–2008, we used both video-monitoring of natural nests and direct observations of predation to identify nest predators of open-cup nesting riparian songbirds along tributaries of Mono Lake, California. Video cameras at...

  19. Predation on simulated duck nests in relation to nest density and landscape structure

    Czech Academy of Sciences Publication Activity Database

    Padyšáková, E.; Šálek, Martin; Poledník, L.; Sedláček, František; Albrecht, Tomáš

    2010-01-01

    Roč. 37, č. 7 (2010), s. 597-603 ISSN 1035-3712 R&D Projects: GA MŠk LC06073 Institutional research plan: CEZ:AV0Z60870520; CEZ:AV0Z60930519 Keywords : density-dependent predation * littoral patch * landscape type * nest predators * nest success * simulated nests Subject RIV: EG - Zoology Impact factor: 1.205, year: 2010

  20. Breeding phenology of birds: mechanisms underlying seasonal declines in the risk of nest predation.

    Directory of Open Access Journals (Sweden)

    Kathi L Borgmann

    Full Text Available Seasonal declines in avian clutch size are well documented, but seasonal variation in other reproductive parameters has received less attention. For example, the probability of complete brood mortality typically explains much of the variation in reproductive success and often varies seasonally, but we know little about the underlying cause of that variation. This oversight is surprising given that nest predation influences many other life-history traits and varies throughout the breeding season in many songbirds. To determine the underlying causes of observed seasonal decreases in risk of nest predation, we modeled nest predation of Dusky Flycatchers (Empidonax oberholseri in northern California as a function of foliage phenology, energetic demand, developmental stage, conspecific nest density, food availability for nest predators, and nest predator abundance. Seasonal variation in the risk of nest predation was not associated with seasonal changes in energetic demand, conspecific nest density, or predator abundance. Instead, seasonal variation in the risk of nest predation was associated with foliage density (early, but not late, in the breeding season and seasonal changes in food available to nest predators. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the risk of nest predation at nests that were near supplemental feeders. Our results suggest that seasonal changes in foliage density and factors associated with changes in food availability for nest predators are important drivers of temporal patterns in risk of avian nest predation.

  1. Breeding phenology of birds: mechanisms underlying seasonal declines in the risk of nest predation.

    Science.gov (United States)

    Borgmann, Kathi L; Conway, Courtney J; Morrison, Michael L

    2013-01-01

    Seasonal declines in avian clutch size are well documented, but seasonal variation in other reproductive parameters has received less attention. For example, the probability of complete brood mortality typically explains much of the variation in reproductive success and often varies seasonally, but we know little about the underlying cause of that variation. This oversight is surprising given that nest predation influences many other life-history traits and varies throughout the breeding season in many songbirds. To determine the underlying causes of observed seasonal decreases in risk of nest predation, we modeled nest predation of Dusky Flycatchers (Empidonax oberholseri) in northern California as a function of foliage phenology, energetic demand, developmental stage, conspecific nest density, food availability for nest predators, and nest predator abundance. Seasonal variation in the risk of nest predation was not associated with seasonal changes in energetic demand, conspecific nest density, or predator abundance. Instead, seasonal variation in the risk of nest predation was associated with foliage density (early, but not late, in the breeding season) and seasonal changes in food available to nest predators. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the risk of nest predation at nests that were near supplemental feeders. Our results suggest that seasonal changes in foliage density and factors associated with changes in food availability for nest predators are important drivers of temporal patterns in risk of avian nest predation.

  2. Predation on artificial nests by marmosets of the genus Callithrix (Primates, Platyrrhini in a Cerrado fragment in Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Marcos Vinícius de Almeida

    2013-03-01

    Full Text Available Although the causes of decline in bird populations in forest fragments are not well known, nest predation seems to play a major role in these events. A way to estimate the relative importance of predation for the reproduction of native birds is the use of artificial nests. Here, there is a report on the high rates of predation on artificial nests by two marmoset species from the genus Callithrix, C. pennicillata and C. jacchus, as well as their hybrid derivatives, in a Cerrado fragment in the state of Sao Paulo, Brazil. By means of artificial nests and quail eggs filled with paraffin, it was possible to identify the marmosets as predators through the bite pattern left on the paraffin. The results suggest a possible occurrence of predation on natural nests. Further studies involving the monitoring of natural nests will be able to confirm the role of marmosets in the decline of bird populations in the study area.

  3. Local habitat and landscape influence predation of bird nests on afforested Mediterranean cropland

    Science.gov (United States)

    Sánchez-Oliver, J. S.; Rey Benayas, J. M.; Carrascal, L. M.

    2014-07-01

    Afforestation programs such as the one promoted by the EU Common Agrarian Policy have contributed to spread tree plantations on former cropland. Nevertheless these afforestations may cause severe damage to open habitat species, especially birds of high conservation value. We investigated predation of artificial bird nests at young tree plantations and at the open farmland habitat adjacent to the tree plantations in central Spain. Predation rates were very high at both tree plantations (95.6%) and open farmland habitat (94.2%) after two and three week exposure. Plantation edge/area ratio and development of the tree canopy decreased predation rates and plantation area and magpie (Pica pica) abundance increased predation rates within tree plantations, which were also affected by land use types around plantations. The area of nearby tree plantations (positive effect), distance to the tree plantation edge (negative effect), and habitat type (mainly attributable to the location of nests in vineyards) explained predation rates at open farmland habitat. We conclude that predation rates on artificial nests were particularly high and rapid at or nearby large plantations, with high numbers of magpies and low tree development, and located in homogenous landscapes dominated by herbaceous crops and pastures with no remnants of semi-natural woody vegetation. Landscape planning should not favour tree plantations as the ones studied here in Mediterranean agricultural areas that are highly valuable for ground-nesting bird species.

  4. Predation of artificial ground nests on white-tailed prairie dog colonies

    Science.gov (United States)

    Baker, B.W.; Stanley, T.R.; Sedgwick, J.A.

    1999-01-01

    Prairie dog (Cynomys spp.) colonies are unique to prairie and shrub-steppe landscapes. However, widespread eradication, habitat loss, and sylvatic plague (Yersinia pestis) have reduced their numbers by 98% since historical times. Birds associated with prairie dogs also are declining. Potential nest predators, such as coyotes (Canis latrans), swift foxes (Vulpes velox), and badgers (Taxidea taxus), may be attracted to colonies where a high concentration of prairie dogs serve as available prey. Increased abundance of small mammals, including prairie dogs, also may increase the risk of predation for birds nesting on colonies. Finally, because grazing by prairie dogs may decrease vegetation height and canopy cover, bird nests may be easier for predators to locate. In this study, we placed 1,444 artificial ground nests on and off 74 white-tailed prairie dog (C. leucurus) colonies to test the hypothesis that nest predation rates are higher on colonies than at nearby off sites (i.e., uncolonized habitat). We sampled colonies from 27 May to 16 July 1997 at the following 3 complexes: Coyote Basin, Utah and Colorado; Moxa Arch, Wyoming; and Shirley Basin, Wyoming. Differences in daily predation rates between colonies and paired off sites averaged 1.0% (P = 0.060). When converted to a typical 14-day incubation period, predation rates averaged 14% higher on colonies (57.7 ?? 2.7%; ?? ?? SE) than at off sites (50.4 ?? 3.1%). Comparisons of habitat variables on colonies to off sites showed percent canopy cover of vegetation was similar (P = 0.114), percent bare ground was higher on colonies (P 0.288). Although we found the risk of nest predation was higher on white-tailed prairie dog colonies than at off sites, fitness of birds nesting on colonies might depend on other factors that influence foraging success, reproductive success, or nestling survival.

  5. Greater sage-grouse nest predators in the Virginia Mountains of northwestern Nevada

    Science.gov (United States)

    Lockyer, Zachary B.; Coates, Peter S.; Casazza, Michael L.; Espinosa, Shawn; Delehanty, David J.

    2013-01-01

    Greater sage-grouse Centrocercus urophasianus, hereafter sage-grouse, populations have declined across their range due to the loss, degradation, and fragmentation of habitat. Habitat alterations can lead not only to vegetative changes but also to shifts in animal behavior and predator composition that may influence population vital rates, such as nest success. For example, common ravens Corvus corax are sage-grouse nest predators, and common raven abundance is positively associated with human-caused habitat alterations. Because nest success is a central component to sage-grouse population persistence, research that identifies factors influencing nest success will better inform conservation efforts. We used videography to unequivocally identify sage-grouse nest predators within the Virginia Mountains of northwestern Nevada, USA, from 2009 to 2011 and used maximum likelihood to calculate daily probability of nest survival. In the Virginia Mountains, fires, energy exploration, and other anthropogenic activities have altered historic sage-grouse habitat. We monitored 71 sage-grouse nests during the study, placing video cameras at 39 nests. Cumulative nest survival for all nests was 22.4% (95% CI, 13.0–33.4%), a survival rate that was significantly lower than other published results for sage-grouse in the Great Basin. Depredation was the primary cause for nest failure in our study (82.5%), and common ravens were the most frequent sage-grouse nest predator, accounting for 46.7% of nest depredations. We also successfully documented a suite of mammalian and reptilian species depredating sage-grouse nests, including some predators never previously confirmed in the literature to be sage-grouse nest predators (i.e., bobcats Lynx rufus and long-tailed weasels Mephitis frenata). Within the high elevation, disturbed habitat of the Virginia Mountains, low sage-grouse nest success may be limiting sage-grouse population growth. These results suggest that management actions that

  6. Does removal of mammalian predators significantly affect success of simulated nests in linear habitats? Case study on American mink Mustela vison \\& Predation on simulated duck nests in relation to nest density and habitat type

    OpenAIRE

    PADYŠÁKOVÁ, Eliška

    2007-01-01

    This thesis is made up of two studies dealing with predation of waterfowl nests. in the first study, we determined wheather removal of introduced predator Mustela vison affected nest survival of simulated duck nests in linear habitat. In the second study, we tested two hypothesis: 1)predation depends on density of waterfowl nests, 2)mammals are main predators in forest habitat and birds mainly depredate nests deployed in open land.

  7. Common, but Commonly Overlooked: Red-bellied Woodpeckers as Songbird Nest Predators

    Science.gov (United States)

    Kirsten R. Hazler; Dawn E.W. Drumtra; Matthew R. Marshall; Robert J. Cooper; Paul B. Hamel

    2004-01-01

    Woodpeckers in North America are not widely recognized as nest predators. In this paper, we describe several eyewitness accounts of songbird nest predation by Red-bellied Woodpeckers (Melanerpes carolinus), document evidence that songbirds recognize woodpeckers as nest predators, and show that our observations are consistent with previously published...

  8. Nest predation risk and growth strategies of passerine species: grow fast or develop traits to escape risk?

    Science.gov (United States)

    Cheng, Yi-Ru; Martin, Thomas E.

    2012-01-01

    Different body components are thought to trade off in their growth and development rates, but the causes for relative prioritization of any trait remains a critical question. Offspring of species at higher risk of predation might prioritize development of locomotor traits that facilitate escaping risky environments over growth of mass. We tested this possibility in 12 altricial passerine species that differed in their risk of nest predation. We found that rates of growth and development of mass, wings, and endothermy increased with nest predation risk across species. In particular, species with higher nest predation risk exhibited relatively faster growth of wings than of mass, fledged with relatively larger wing sizes and smaller mass, and developed endothermy earlier at relatively smaller mass. This differential development can facilitate both escape from predators and survival outside of the nest environment. Tarsus growth was not differentially prioritized with respect to nest predation risk, and instead all species achieved adult tarsus size by age of fledging. We also tested whether different foraging modes (aerial, arboreal, and ground foragers) might explain the variation of differential growth of locomotor modules, but we found that little residual variation was explained. Our results suggest that differences in nest predation risk among species are associated with relative prioritization of body components to facilitate escape from the risky nest environment.

  9. Coping with shifting nest predation refuges by European reed Warblers Acrocephalus scirpaceus.

    Directory of Open Access Journals (Sweden)

    Lucyna Halupka

    Full Text Available Predation, the most important source of nest mortality in altricial birds, has been a subject of numerous studies during past decades. However, the temporal dynamics between changing predation pressures and parental responses remain poorly understood. We analysed characteristics of 524 nests of European reed warblers monitored during six consecutive breeding seasons in the same area, and found some support for the shifting nest predation refuge hypothesis. Nest site characteristics were correlated with nest fate, but a nest with the same nest-site attributes could be relatively safe in one season and vulnerable to predation in another. Thus nest predation refuges were ephemeral and there was no between-season consistency in nest predation patterns. Reed warblers that lost their first nests in a given season did not disperse farther for the subsequent reproductive attempt, compared to successful individuals, but they introduced more changes to their second nest sites. In subsequent nests, predation risk remained constant for birds that changed nest-site characteristics, but increased for those that did not. At the between-season temporal scale, individual birds did not perform better with age in terms of reducing nest predation risk. We conclude that the experience acquired in previous years may not be useful, given that nest predation refuges are not stable.

  10. Sharp-Tailed Grouse Nest Survival and Nest Predator Habitat Use in North Dakota's Bakken Oil Field.

    Directory of Open Access Journals (Sweden)

    Paul C Burr

    Full Text Available Recent advancements in extraction technologies have resulted in rapid increases of gas and oil development across the United States and specifically in western North Dakota. This expansion of energy development has unknown influences on local wildlife populations and the ecological interactions within and among species. Our objectives for this study were to evaluate nest success and nest predator dynamics of sharp-tailed grouse (Tympanuchus phasianellus in two study sites that represented areas of high and low energy development intensities in North Dakota. During the summers of 2012 and 2013, we monitored 163 grouse nests using radio telemetry. Of these, 90 nests also were monitored using miniature cameras to accurately determine nest fates and identify nest predators. We simultaneously conducted predator surveys using camera scent stations and occupancy modeling to estimate nest predator occurrence at each site. American badgers (Taxidea taxus and striped skunks (Mephitis mephitis were the primary nest predators, accounting for 56.7% of all video recorded nest depredations. Nests in our high intensity gas and oil area were 1.95 times more likely to succeed compared to our minimal intensity area. Camera monitored nests were 2.03 times more likely to succeed than non-camera monitored nests. Occupancy of mammalian nest predators was 6.9 times more likely in our study area of minimal gas and oil intensity compared to the high intensity area. Although only a correlative study, our results suggest energy development may alter the predator community, thereby increasing nest success for sharp-tailed grouse in areas of intense development, while adjacent areas may have increased predator occurrence and reduced nest success. Our study illustrates the potential influences of energy development on the nest predator-prey dynamics of sharp-tailed grouse in western North Dakota and the complexity of evaluating such impacts on wildlife.

  11. Variation in nest predation among arid-zone birds | Lloyd | Ostrich ...

    African Journals Online (AJOL)

    I examined the nesting habits and success of 11 co-existing species in an arid, sub-tropical habitat in South Africa. Nesting success ranged from 3.5% to 75.4% among species, with predation by mammals and snakes accounting for 94% of nest losses. Differences in predator avoidance behaviour (deserting the nest vs ...

  12. Synchronisation of parental behaviours reduces the risk of nest predation in a socially monogamous passerine bird.

    Science.gov (United States)

    Leniowski, K; Węgrzyn, E

    2018-05-09

    Social monogamy with bi-parental care is the most common breeding pattern in birds, yet cooperation between mates has not been intensively studied to date. In this study we investigate synchronisation of parental behaviours in the blackcap Sylvia atricapilla, a species characterized by bi-parental care and high nest predation. We test the hypothesis that mates synchronize their behaviours to decrease total activity at the nest, which is known to affect predation rate in birds. We examine if blackcap parents synchronise their feeding trips more when nestlings are at the poikilothermic stage, and they may be more vulnerable to nest predation due to their inability to escape and survive outside the nest without parental brooding. We also investigate the alternation of feeding trips by parents. We show that blackcap parents synchronise the majority of their feeding trips during the whole nestling period, and the level of parental synchrony is higher before nestlings develop endothermy. The alternation of male and female feeding trips was much higher than would be expected by chance and was positively related to parental synchrony. We have demonstrated that synchronisation of parental feeding trips significantly decreased parental activity at the nest, and nest survival time increased with the synchrony of parental feeding trips.

  13. Landscape-moderated bird nest predation in hedges and forest edges

    Science.gov (United States)

    Ludwig, Martin; Schlinkert, Hella; Holzschuh, Andrea; Fischer, Christina; Scherber, Christoph; Trnka, Alfréd; Tscharntke, Teja; Batáry, Péter

    2012-11-01

    Landscape-scale agricultural intensification has caused severe declines in biodiversity. Hedges and forest remnants may mitigate biodiversity loss by enhancing landscape heterogeneity and providing habitat to a wide range of species, including birds. However, nest predation, the major cause of reproductive failure of birds, has been shown to be higher in forest edges than in forest interiors. Little is known about how spatial arrangement (configuration) of hedges affects the avian nest predation. We performed an experiment with artificial ground and elevated nests (resembling yellowhammer and whitethroat nests) baited with quail and plasticine eggs. Nests were placed in three habitat types with different degrees of isolation from forests: forest edges, hedges connected to forests and hedges isolated from forests. Nest predation was highest in forest edges, lowest in hedges connected to forests and intermediate in isolated hedges. In the early breeding season, we found similar nest predation on ground and elevated nests, but in the late breeding season nest predation was higher on ground nests than on elevated nests. Small mammals were the main predators of ground nests and appeared to be responsible for the increase in predation from early to late breeding season, whereas the elevated nests were mainly depredated by small birds and small mammals. High predation pressure at forest edges was probably caused by both forest and open-landscape predators. The influence of forest predators may be lower at hedges, leading to lower predation pressure than in forest edges. Higher predation pressure in isolated than connected hedges might be an effect of concentration of predators in these isolated habitats. We conclude that landscape configuration of hedges is important in nest predation, with connected hedges allowing higher survival than isolated hedges and forest edges.

  14. Evolution of nesting height in an endangered Hawaiian forest bird in response to a non-native predator.

    Science.gov (United States)

    Vanderwerf, Eric A

    2012-10-01

    The majority of bird extinctions since 1800 have occurred on islands, and non-native predators have been the greatest threat to the persistence of island birds. Island endemic species often lack life-history traits and behaviors that reduce the probability of predation and they can become evolutionarily trapped if they are unable to adapt, but few studies have examined the ability of island species to respond to novel predators. The greatest threat to the persistence of the Oahu Elepaio (Chasiempis ibidis), an endangered Hawaiian forest bird, is nest predation by non-native black rats (Rattus rattus). I examined whether Oahu Elepaio nest placement has changed at the individual and population levels in response to rat predation by measuring nest height and determining whether each nest produced offspring from 1996 to 2011. Average height of Oahu Elepaio nests increased 50% over this 16-year period, from 7.9 m (SE 1.7) to 12.0 m (SE 1.1). There was no net change in height of sequential nests made by individual birds, which means individual elepaios have not learned to place nests higher. Nests ≤3 m off the ground produced offspring less often, and the proportion of such nests declined over time, which suggests that nest-building behavior has evolved through natural selection by predation. Nest success increased over time, which may increase the probability of long-term persistence of the species. Rat control may facilitate the evolution of nesting height by slowing the rate of population decline and providing time for this adaptive response to spread through the population. ©2012 Society for Conservation Biology.

  15. Effects of intraguild predators on nest-site selection by prey.

    Science.gov (United States)

    Huang, Wen-San; Pike, David A

    2012-01-01

    Nest-site selection involves tradeoffs between the risk of predation (on females and/or nests) and nest-site quality (microenvironment), and consequently suitable nesting sites are often in limited supply. Interactions with "classical" predators (e.g., those not competing for shared resources) can strongly influence nest-site selection, but whether intraguild predation also influences this behavior is unknown. We tested whether risk of predation from an intraguild predator [the diurnal scincid lizard Eutropis (Mabuya) longicaudata] influences nest-site selection by its prey (the nocturnal gecko Gekko hokouensis) on Orchid Island, Taiwan. These two species putatively compete for shared resources, including invertebrate prey and nesting microhabitat, but the larger E. longicaudata also predates G. hokouensis (but not its hard-shelled eggs). Both species nested within a concrete wall containing a series of drainage holes that have either one ("closed-in") or two openings ("open"). In allopatry, E. longicaudata preferred to nest within holes that were plugged by debris (thereby protecting eggs from water intrusion), whereas G. hokouensis selected holes that were open at both ends (facilitating escape from predators). When we experimentally excluded E. longicaudata from its preferred nesting area, G. hokouensis not only nested in higher abundances, but also modified its nest-site selection, such that communal nesting was more prevalent and both open and closed-in holes were used equally. Egg viability was unaffected by the choice of hole type, but was reduced slightly (by 7%) in the predator exclusion area (presumably due to higher local incubation temperatures). Our field experiment demonstrates that intraguild predators can directly influence the nest density of prey by altering maternal nest-site selection behavior, even when the predator and prey are active at different times of day and the eggs are not at risk of predation.

  16. Is it safe to nest near conspicuous neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nests

    OpenAIRE

    Marie-Andrée Giroux; Myriam Trottier-Paquet; Joël Bêty; Vincent Lamarre; Nicolas Lecomte

    2016-01-01

    Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, selecting nest sites protected from predators, and nesting in association with protective species. American Golden-Plovers (Pluvialis dominica) defend their territory by using various warning and distraction behaviours displayed at varying levels of intensity (hereafter ?conspicuous ...

  17. Nest site selection in a hot desert : Trade-off between microclimate and predation risk?

    NARCIS (Netherlands)

    Tieleman, B. Irene; van Noordwijk, Hendrika J.; Williams, Joseph B.

    Nest placement affects the risk of predation on both eggs and incubating parents and determines the microclimate for incubation, two functions that may be in conflict, especially in hot deserts. We studied the roles of microclimate and nest predation on nest site selection by Hoopoe Larks (Alaemon

  18. Nest predation and reproductive traits in small passerines: a comparative approach

    Science.gov (United States)

    Yanes, Miguel; Suárez, Francisco

    Nest predation can be a decisive factor in the evolution of bird reproduction strategies. This paper compares several reproductive traits in small passerines on the Iberian Peninsula (n=31) with the probability of daily nest survival from predation. We consider the phylogenetic relationships between species by means of an analysis according to three models of evolutionary change: Brownian, punctuational and GRAFEN'S arbitrary. In this comparative evolutionary scenario, clutch size, egg volume and incubation period appear not to change in relation to nest predation, while the nestling phase duration is a positively-related parameter to daily nest survival from predation. These results are consistent for all models of evolutionary change. Thus, from the perspective of nest predation, the nestling period is the most important evolutionary parameter in small passerines. A hypothetical influence of nest predation on passerine clutch and egg size should only be regarded as an indirect factor, linked to the relationship between these parameters and the duration of the nestling period.

  19. Human disturbances and predation on artificial ground nests across an urban gradient

    OpenAIRE

    Bocz, R.; Szép, D.; Witz, D.; Ronczyk, L.; Kurucz, K.; Purger, J. J.

    2017-01-01

    In our study with artificial nests we observed that the absence of ground nesting bird species in the city centre and in residential districts was due to disturbance by humans and domestic animals (dogs and cats) rather than to predation. Furthermore, predation pressure was higher in the outskirts of the city due to the greater number of natural predators. Our results suggest that planning and creating undisturbed areas could increase the chances of ground nesting birds settling and breeding ...

  20. Nest site selection by Kentish plover suggests a trade-off between nest-crypsis and predator detection strategies.

    Directory of Open Access Journals (Sweden)

    Miguel Ángel Gómez-Serrano

    Full Text Available Predation is one of the main causes of adult mortality and breeding failure for ground-nesting birds. Micro-habitat structure around nests plays a critical role in minimizing predation risk. Plovers nest in sites with little vegetation cover to maximize the incubating adult visibility, but many studies suggest a trade-off between nest-crypsis and predator detection strategies. However, this trade-off has not been explored in detail because methods used so far do not allow estimating the visibility with regards to critical factors such as slope or plant permeability to vision. Here, we tested the hypothesis that Kentish plovers select exposed sites according to a predator detection strategy, and the hypothesis that more concealed nests survive longer according to a crypsis strategy. To this end, we obtained an accurate estimation of the incubating adult's field of vision through a custom built inverted periscope. Our results showed that plovers selected nest sites with higher visibility than control points randomly selected with regards to humans and dogs, although nests located in sites with higher vegetation cover survived longer. In addition, the flushing distance (i.e., the distance at which incubating adults leave the nest when they detect a potential predator decreased with vegetation cover. Consequently, the advantages of concealing the nest were limited by the ability to detect predators, thus indirectly supporting the existence of the trade-off between crypsis and predator detection. Finally, human disturbance also constrained nest choice, forcing plovers to move to inland sites that were less suitable because of higher vegetation cover, and modulated flushing behavior, since plovers that were habituated to humans left their nests closer to potential predators. This constraint on the width of suitable breeding habitat is particularly relevant for the conservation of Kentish Plover in sand beaches, especially under the current context of

  1. Linking snake behavior to nest predation in a Midwestern bird community.

    Science.gov (United States)

    Weatherhead, Patrick J; Carfagno, Gerardo L F; Sperry, Jinelle H; Brawn, Jeffrey D; Robinson, Scott K

    2010-01-01

    Nest predators can adversely affect the viability of songbird populations, and their impact is exacerbated in fragmented habitats. Despite substantial research on this predator-prey interaction, however, almost all of the focus has been on the birds rather than their nest predators, thereby limiting our understanding of the factors that bring predators and nests into contact. We used radiotelemetry to document the activity of two snake species (rat snakes, Elaphe obsoleta; racers, Coluber constrictor) known to prey on nests in Midwestern bird communities and simultaneously monitored 300 songbird nests and tested the hypothesis that predation risk should increase for nests when snakes were more active and in edge habitat preferred by both snake species. Predation risk increased when rat snakes were more active, for all nests combined and for two of the six bird species for which we had sufficient nests to allow separate analyses. This result is consistent with rat snakes being more important nest predators than racers. We found no evidence, however, that nests closer to forest edges were at greater risk. These results are generally consistent with the one previous study that investigated rat snakes and nest predation simultaneously. The seemingly paradoxical failure to find higher predation risk in the snakes' preferred habitat (i.e., edge) might be explained by the snakes using edges at least in part for non-foraging activities. We propose that higher nest predation in fragmented habitats (at least that attributable to snakes) results indirectly from edges promoting larger snake populations, rather than from edges directly increasing the risk of nest predation by snakes. If so, the notion of edges per se functioning as ecological "traps" merits further study.

  2. Can variation in risk of nest predation explain altitudinal migration in tropical birds?

    Science.gov (United States)

    Boyle, W Alice

    2008-03-01

    Migration is among the best studied of animal behaviors, yet few empirical studies have tested hypotheses explaining the ultimate causes of these cyclical annual movements. Fretwell's (1980) hypothesis predicts that if nest predation explains why many tropical birds migrate uphill to breed, then predation risk must be negatively associated with elevation. Data from 385 artificial nests spanning 2,740 m of elevation on the Atlantic slope of Costa Rica show an overall decline in predation with increasing elevation. However, nest predation risk was highest at intermediate elevations (500-650 m), not at lowest elevations. The proportion of nests depredated by different types of predators differed among elevations. These results imply that over half of the altitudinal migrant bird species in this region migrate to safer breeding areas than their non-breeding areas, suggesting that variation in nest predation risk could be an important benefit of uphill migrations of many species.

  3. Light pollution affects nesting behavior of loggerhead turtles and predation risk of nests and hatchlings.

    Science.gov (United States)

    Silva, Elton; Marco, Adolfo; da Graça, Jesemine; Pérez, Héctor; Abella, Elena; Patino-Martinez, Juan; Martins, Samir; Almeida, Corrine

    2017-08-01

    The introduction of artificial light into wildlife habitats is a rapidly expanding aspect of global change, which has many negative impacts on a wide range of taxa. In this experimental study, which took place on a beach located on the island of Boa Vista (Cabo Verde), three types of artificial light were tested on nesting loggerhead sea turtles as well as on ghost crabs, which intensively predate on nests and hatchlings, to determine the effects they would produce on the behavior of both species. Over the course of 36days, female loggerheads and ghost crabs were studied under yellow, orange and red lights, with observations also being made on dark nights that served as a control treatment. During this period, the frequencies of nesting attempts, the time taken by turtles to complete each phase of the nesting process, and ghost crab abundance and behaviors were carefully recorded. 1146 loggerhead nesting attempts were observed and recorded during the experiments, and results showed a decrease in nesting attempts of at least 20% when artificial lighting was present. A significant decline in successful attempts was also observed within the central sections of the beach, which corresponded to those that received more light. This artificial lighting significantly increased the time that turtles spent on the nesting process and forced them to do more extensive beach crawls. Despite this, the presence of light had no apparent effect on the final selection of the nesting site. Yellow and orange lights significantly disrupted the sea finding behavior and turtles were often unable to orient themselves seaward under these color lights. Disoriented turtles were observed crawling in circuitous paths in front of the light source for several minutes. In addition, artificial lights had the potential to increase the number of ghost crabs present within the illuminated stretches of the beach. However, only yellow lighting produced a significant change on aggressive and prey

  4. Predator removal and nesting waterbird success at San Francisco Bay, California

    Science.gov (United States)

    Meckstroth, A.M.; Miles, A.K.

    2005-01-01

    The efficacy of long-term predator removal in urbanized areas is poorly understood. The impact of predation on ground-nesting waterbirds, as well as predator abundance and composition in predator removal versus non-removal or reference sites were examined at South San Francisco Bay. The success of natural nests and predator activity was monitored using track plates, trip cameras, wire haircatchers and simulated nests. Removal sites had higher nest densities, but lower hatching success than reference sites. Predator composition and abundance were not different at the removal and reference sites for any predator other than feral Cat (Felis domesticus). Striped Skunk (Mephitis mephitis) comprised the majority (84%) of predators removed, yet remained the most abundant predators in removal and reference sites. Urban environments provide supplemental food that may influence skunks and other nest predators to immigrate into vacancies created by predator removal. Based on the findings from this study, predator removal should be applied intensively over a larger geographic area in order to be a viable management strategy for some mammalian species in urbanized areas.

  5. Who are the important predators of sea turtle nests at Wreck Rock beach?

    Science.gov (United States)

    Lei, Juan; Booth, David T

    2017-01-01

    Excessive sea turtle nest predation is a problem for conservation management of sea turtle populations. This study assessed predation on nests of the endangered loggerhead sea turtle ( Caretta caretta ) at Wreck Rock beach adjacent to Deepwater National Park in Southeast Queensland, Australia after a control program for feral foxes was instigated. The presence of predators on the nesting dune was evaluated by tracking plots (2 × 1 m) every 100 m along the dune front. There were 21 (2014-2015) and 41 (2015-2016) plots established along the dune, and these were monitored for predator tracks daily over three consecutive months in both nesting seasons. Predator activities at nests were also recorded by the presence of tracks on top of nests until hatchlings emerged. In addition, camera traps were set to record the predator activity around selected nests. The tracks of the fox ( Vulpes vulpes ) and goanna ( Varanus spp ) were found on tracking plots. Tracking plots, nest tracks and camera traps indicated goanna abundance varied strongly between years. Goannas were widely distributed along the beach and had a Passive Activity Index (PAI) (0.31 in 2014-2015 and 0.16 in 2015-2016) approximately seven times higher than that of foxes (PAI 0.04 in 2014-2015 and 0.02 in 2015-2016). Five hundred and twenty goanna nest visitation events were recorded by tracks but no fox tracks were found at turtle nests. Camera trap data indicated that yellow-spotted goannas ( Varanus panoptes ) appeared at loggerhead turtle nests more frequently than lace monitors ( V. varius ) did, and further that lace monitors only predated nests previously opened by yellow-spotted goannas. No foxes were recorded at nests with camera traps. This study suggests that large male yellow-spotted goannas are the major predator of sea turtle nests at the Wreck Rock beach nesting aggregation and that goanna activity varies between years.

  6. Who are the important predators of sea turtle nests at Wreck Rock beach?

    Directory of Open Access Journals (Sweden)

    Juan Lei

    2017-06-01

    Full Text Available Excessive sea turtle nest predation is a problem for conservation management of sea turtle populations. This study assessed predation on nests of the endangered loggerhead sea turtle (Caretta caretta at Wreck Rock beach adjacent to Deepwater National Park in Southeast Queensland, Australia after a control program for feral foxes was instigated. The presence of predators on the nesting dune was evaluated by tracking plots (2 × 1 m every 100 m along the dune front. There were 21 (2014–2015 and 41 (2015–2016 plots established along the dune, and these were monitored for predator tracks daily over three consecutive months in both nesting seasons. Predator activities at nests were also recorded by the presence of tracks on top of nests until hatchlings emerged. In addition, camera traps were set to record the predator activity around selected nests. The tracks of the fox (Vulpes vulpes and goanna (Varanus spp were found on tracking plots. Tracking plots, nest tracks and camera traps indicated goanna abundance varied strongly between years. Goannas were widely distributed along the beach and had a Passive Activity Index (PAI (0.31 in 2014–2015 and 0.16 in 2015–2016 approximately seven times higher than that of foxes (PAI 0.04 in 2014–2015 and 0.02 in 2015–2016. Five hundred and twenty goanna nest visitation events were recorded by tracks but no fox tracks were found at turtle nests. Camera trap data indicated that yellow-spotted goannas (Varanus panoptes appeared at loggerhead turtle nests more frequently than lace monitors (V. varius did, and further that lace monitors only predated nests previously opened by yellow-spotted goannas. No foxes were recorded at nests with camera traps. This study suggests that large male yellow-spotted goannas are the major predator of sea turtle nests at the Wreck Rock beach nesting aggregation and that goanna activity varies between years.

  7. Rhodamine-Injected Eggs to Photographically Identify Small Nest-Predators

    Science.gov (United States)

    Thomas J. Maier; Richard M. DeGraaf

    2000-01-01

    Photographs that clearly disclose avian-nest predators are difficult to obtain, particularly when predators are small and exhibit subtle depredatory behavior. We exposed House Sparrow (Passer domesticus) eggs injected with Rhodamine B dye in camera-monitored ground nests for 12-d periods at 76 sites within mixed-hardwood forest stands in central...

  8. Is it safe to nest near conspicuous neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nests

    Directory of Open Access Journals (Sweden)

    Marie-Andrée Giroux

    2016-08-01

    Full Text Available Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, selecting nest sites protected from predators, and nesting in association with protective species. American Golden-Plovers (Pluvialis dominica defend their territory by using various warning and distraction behaviours displayed at varying levels of intensity (hereafter “conspicuous behaviour”, as well as more aggressive behaviours such as aerial attacks, but only in some populations. Such antipredator behaviour has the potential to repel predators and thus benefit the neighbouring nests by decreasing their predation risk. Yet, conspicuous behaviour could also attract predators by signalling the presence of a nest. To test for the existence of a protective effect associated with the conspicuous antipredator behaviour of American Golden-Plovers, we studied the influence of proximity to plover nests on predation risk of artificial nests on Igloolik Island (Nunavut, Canada in July 2014. We predicted that the predation risk of artificial nests would decrease with proximity to and density of plover nests. We monitored 18 plover nests and set 35 artificial nests at 30, 50, 100, 200, and 500 m from seven of those plover nests. We found that the predation risk of artificial nests increases with the density of active plover nests. We also found a significant negative effect of the distance to the nearest active protector nest on predation risk of artificial nests. Understanding how the composition and structure of shorebird communities generate spatial patterns in predation risks represents a key step to better understand the importance of these species of conservation concern in tundra food webs.

  9. Is it safe to nest near conspicuous neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nests.

    Science.gov (United States)

    Giroux, Marie-Andrée; Trottier-Paquet, Myriam; Bêty, Joël; Lamarre, Vincent; Lecomte, Nicolas

    2016-01-01

    Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, selecting nest sites protected from predators, and nesting in association with protective species. American Golden-Plovers (Pluvialis dominica) defend their territory by using various warning and distraction behaviours displayed at varying levels of intensity (hereafter "conspicuous behaviour"), as well as more aggressive behaviours such as aerial attacks, but only in some populations. Such antipredator behaviour has the potential to repel predators and thus benefit the neighbouring nests by decreasing their predation risk. Yet, conspicuous behaviour could also attract predators by signalling the presence of a nest. To test for the existence of a protective effect associated with the conspicuous antipredator behaviour of American Golden-Plovers, we studied the influence of proximity to plover nests on predation risk of artificial nests on Igloolik Island (Nunavut, Canada) in July 2014. We predicted that the predation risk of artificial nests would decrease with proximity to and density of plover nests. We monitored 18 plover nests and set 35 artificial nests at 30, 50, 100, 200, and 500 m from seven of those plover nests. We found that the predation risk of artificial nests increases with the density of active plover nests. We also found a significant negative effect of the distance to the nearest active protector nest on predation risk of artificial nests. Understanding how the composition and structure of shorebird communities generate spatial patterns in predation risks represents a key step to better understand the importance of these species of conservation concern in tundra food webs.

  10. Managing individual nests promotes population recovery of a top predator

    Science.gov (United States)

    Cruz, Jennyffer; Windels, Steve K.; Thogmartin, Wayne E.; Crimmins, Shawn M.; Grim, Leland; Zuckerberg, Benjamin

    2018-01-01

    Threatened species are managed using diverse conservation tactics implemented at multiple scales ranging from protecting individuals, to populations, to entire species. Individual protection strives to promote recovery at the population‐ or species‐level, although this is seldom evaluated.After decades of widespread declines, bald eagles, Haliaeetus leucocephalus, are recovering throughout their range due to legal protection and pesticide bans. However, like other raptors, their recovery remains threatened by human activities. Bald eagle nests are commonly managed using buffer zones to minimize human disturbance, but the benefits of this practice remain unquantified.Within Voyageurs National Park (VNP), Minnesota, USA, managers have monitored bald eagle populations for over 40 years, and since 1991, have protected at‐risk nests from human disturbance using buffer zones (200 and 400 m radius). We aimed to (1) quantify the recovery of bald eagles in VNP (1973–2016), and (2) provide a first‐ever evaluation of the individual‐ and population‐level effects of managing individual nests. To do so, we developed Bayesian Integrated Population Models combining observations of nest occupancy and reproductive output (metrics commonly collected for raptors) to estimate nest‐level probabilities of occupancy, nest success, and high productivity (producing ≥2 nestlings), as well as population‐level estimates of abundance and growth.The breeding population of bald eagles at VNP increased steadily from management significantly improved occupancy and success. At the population‐level, management led to 8% and 13% increases in nest success and productivity rates, respectively, resulting in a 37% increase in breeding pair abundance.Synthesis and applications. There is a clear need to evaluate how management approaches at multiple scales assist in species recovery. Our study uses an Integrated Population Model to reveal the population‐level benefits of a widely

  11. Edge, height and visibility effects on nest predation by birds and mammals in the Brazilian cerrado

    Science.gov (United States)

    Dodonov, Pavel; Paneczko, Ingrid Toledo; Telles, Marina

    2017-08-01

    Edge influence is one of the main impacts in fragmented landscapes; yet, most of studies on edge influence have focused on high-contrast edges, and the impacts of low-contrast edges and narrow linear openings are less understood. Edge influence often affects bird nest predation, but these effects are not ubiquitous and may depend on characteristics such as nest height and visibility. We performed an experiment on nest predation in a migratory passerine, Elaenia chiriquensis (Lesser Elaenia; Passeriformes: Tyrannidae), in a savanna vegetation of the Brazilian Cerrado biome in South-Eastern Brazil. We used 89 real E. chiriquensis nests, collected during previous reproductive seasons, with two plasticine eggs in each, and randomly distributed them at two locations (edge - up to 20 m from a firebreak edge and interior - approx. 150-350 m from the edge) and two heights (low - 60-175 cm and high - 190-315 cm above ground). We also measured leaf and branch density around each nest. We performed this study on two 15-days campaigns, checking the nests every 2-3 days and removing those with predation marks. We sorted the predation marks into those made by birds, mammals, or unidentified predators, and used generalized linear models to assess the effects of location, height and leaf density on survival time and predator type. Only four nests had not been predated during the experiment; 55 nests were predated by birds, 7 by mammals, and 23 by unidentified predators. Low nests in the interior tended to have larger survival times whereas high nests at the edge tended to be more predated by birds and less predated by mammals. Thus, even a low-contrast (firebreak) edge may significantly increase nest predation, which is also affected by the nest's height, mainly due to predation by birds. These effects may be due to predator movement along the edge as well as to edge-related changes in vegetation structure. We suggest that higher-contrast edges which may also be used as movement

  12. Parents or predators: Examining intraseasonal variation in nest survival for migratory passerine

    Science.gov (United States)

    Robin Hirsch-Jacobson; W. Andrew Cox; Emily E. Tewes; Frank R., III Thompson; John. Faaborg

    2012-01-01

    For birds, risk of nest predation can vary within a breeding season, but few data exist that explain why such variation occurs. We investigated intraseasonal variation of nest survival of the Acadian Flycatcher (Empidonax virescens) in Midwestern forests and tested whether four of the adults' reproductive strategies (clutch size, nest...

  13. Ocean acidification alters predator behaviour and reduces predation rate.

    Science.gov (United States)

    Watson, Sue-Ann; Fields, Jennifer B; Munday, Philip L

    2017-02-01

    Ocean acidification poses a range of threats to marine invertebrates; however, the emerging and likely widespread effects of rising carbon dioxide (CO 2 ) levels on marine invertebrate behaviour are still little understood. Here, we show that ocean acidification alters and impairs key ecological behaviours of the predatory cone snail Conus marmoreus Projected near-future seawater CO 2 levels (975 µatm) increased activity in this coral reef molluscivore more than threefold (from less than 4 to more than 12 mm min -1 ) and decreased the time spent buried to less than one-third when compared with the present-day control conditions (390 µatm). Despite increasing activity, elevated CO 2 reduced predation rate during predator-prey interactions with control-treated humpbacked conch, Gibberulus gibberulus gibbosus; 60% of control predators successfully captured and consumed their prey, compared with only 10% of elevated CO 2 predators. The alteration of key ecological behaviours of predatory invertebrates by near-future ocean acidification could have potentially far-reaching implications for predator-prey interactions and trophic dynamics in marine ecosystems. Combined evidence that the behaviours of both species in this predator-prey relationship are altered by elevated CO 2 suggests food web interactions and ecosystem structure will become increasingly difficult to predict as ocean acidification advances over coming decades. © 2017 The Author(s).

  14. Female in-nest chatter song increases predation

    OpenAIRE

    Kleindorfer, Sonia; Evans, Christine; Mahr, Katharina

    2016-01-01

    Female song is an ancestral trait in songbirds, yet extant females generally sing less than males. Here, we examine sex differences in the predation cost of singing behaviour. The superb fairy-wren (Malurus cyaneus) is a Southern Hemisphere songbird; males and females provision the brood and produce solo song year-round. Both sexes had higher song rate during the fertile period and lower song rate during incubation and chick feeding. Females were more likely than males to sing close to or ins...

  15. Human disturbances and predation on artificial ground nests across an urban gradient

    Directory of Open Access Journals (Sweden)

    Bocz, R.

    2017-03-01

    Full Text Available In our study with artificial nests we observed that the absence of ground nesting bird species in the city centre and in residential districts was due to disturbance by humans and domestic animals (dogs and cats rather than to predation. Furthermore, predation pressure was higher in the outskirts of the city due to the greater number of natural predators. Our results suggest that planning and creating undisturbed areas could increase the chances of ground nesting birds settling and breeding in human–dominated landscapes.

  16. Local habitat disturbance increases bird nest predation in the Brazilian Atlantic rainforest

    Directory of Open Access Journals (Sweden)

    Rodrigues, V. B.

    2018-01-01

    Full Text Available We evaluated the effect of anthropogenic disturbance on nest predation in Brazilian Atlantic forest. Artificial nests were distributed in fragments with distinct degrees of anthropogenic disturbance. We found a higher proportion of egg predation on the ground and in the fragments classified as ‘high’ and ‘medium’ disturbance than in the fragments classified as ‘low’ degree of disturbance. The higher egg predation is probably linked to low structural complexity of vegetation and high accessibility of these areas to opportunistic predators. We suggest that forest fragments with high vegetation complexity and low human activity should be preserved in order to maintain the biodiversity of bird species.

  17. Species Diversity Enhances Predator Growth Rates

    International Nuclear Information System (INIS)

    Olson, M.H.; Jacobs, R.P.; O'Donnell, E.B.

    2007-01-01

    Predators can be important top-down regulators of community structure and are known to have both positive and negative effects on species diversity. However, little is known about the reciprocal effects of species diversity on predators. Across a set of 80 lakes in Connecticut, USA, we found a strong positive correlation between prey species diversity (using the Shannon-Weiner Diversity Index) and growth rates of largemouth bass (Micropterus salmoides). This correlation was strongest for small predators and decreased with body size. Although the underlying mechanisms are not known, the correlation is not driven by total fish abundance, predator abundance, or productivity.

  18. Bird's nesting success and eggs predation within Arusa National ...

    African Journals Online (AJOL)

    Identification of predators was obtained indirectly through punched signs left by predators on artificial and true eggs. Observation was done daily and data were analyzed both qualitatively and quantitatively. The study showed no significant difference in predation effect on eggs in glade versus glade edge X2 = 3.08, Df = 1, ...

  19. Passeriformes: nest predators and prey in a Neotropical Savannah in Central Brazil

    Directory of Open Access Journals (Sweden)

    Leonardo F. França

    2009-12-01

    Full Text Available The identification of predators of birds' nests, crucial to a better understanding of predator-prey interactions, remains poorly known. Here we provide evidence that birds, and especially passerines, may depredate birds' nests in the Cerrado (Neotropical Savannah of Central Brazil. Data was collected primarily in a Conservation Unit (Estação Ecológica de Águas Emendadas during the breeding season, between 2003 and 2007. We report and discuss details on 14 events of nest predation, 12 of which by passerines, mostly by curl-crested jays - Cyanocorax cristatellus (Temminck, 1823. The results of our study suggest that the role of birds as nest predators in the Cerrado has been underestimated and needs to be further investigated.

  20. Hypoxia increases the risk of egg predation in a nest-guarding fish

    DEFF Research Database (Denmark)

    Olsson, Karin; Kvarnemo, Charlotta; Andrén, Maria Norevik

    2016-01-01

    For fish with parental care, a nest should meet both the oxygenation needs of the eggs and help protect them against predators. While a small nest opening facilitates the latter, it impedes the former and vice versa. We investigated how the presence of potential egg predators in the form of shore...... in high oxygen reduced fanning, males in low oxygen did not. Filial cannibalism was unaffected by treatment. Sand gobies thus prioritize egg ventilation over the protection afforded by small nest openings under hypoxia and adopt defensive behaviour to avert predator attention, even though this does...... crabs Carcinus maenas affects nest building, egg fanning, defensive displays and filial cannibalism of egg-guarding male sand gobies Pomatoschistus minutus under two levels of dissolved oxygen. In the high oxygen treatment, males retained their nest opening size in the presence of crabs, while males...

  1. Influence of human development and predators on nest survival of tundra birds, Arctic Coastal Plain, Alaska.

    Science.gov (United States)

    Liebezeit, J R; Kendall, S J; Brown, S; Johnson, C B; Martin, P; McDonald, T L; Payer, D C; Rea, C L; Streever, B; Wildman, A M; Zack, S

    2009-09-01

    Nest predation may influence population dynamics of birds on the Arctic Coastal Plain (ACP) of Alaska, USA. Anthropogenic development on the ACP is increasing, which may attract nest predators by providing artificial sources of food, perches, den sites, and nest sites. Enhanced populations or concentrations of human-subsidized predators may reduce nest survival for tundra-nesting birds. In this study, we tested the hypothesis that nest survival decreases in proximity to human infrastructure. We monitored 1257 nests of 13 shorebird species and 619 nests of four passerine species at seven sites on the ACP from 2002 to 2005. Study sites were chosen to represent a range of distances to infrastructure from 100 m to 80 km. We used Cox proportional hazards regression models to evaluate the effects of background (i.e., natural) factors and infrastructure on nest survival. We documented high spatial and temporal variability in nest survival, and site and year were both included in the best background model. We did not detect an effect of human infrastructure on nest survival for shorebirds as a group. In contrast, we found evidence that risk of predation for passerine nests increased within 5 km of infrastructure. This finding provides quantitative evidence of a relationship between infrastructure and nest survival for breeding passerines on the ACP. A posteriori finer-scale analyses (within oil field sites and individual species) suggested that Red and Red-necked Phalaropes combined (Phalaropus fulicarius, P. lobatus) had lower productivity closer to infrastructure and in areas with higher abundance of subsidized predators. However, we did not detect such a relationship between infrastructure and nest survival for Semipalmated and Pectoral Sandpipers (Calidris pusilla, C. melanotos), the two most abundant shorebirds. High variability in environmental conditions, nest survival, and predator numbers between sites and years may have contributed to these inconsistent results

  2. The effects of temperature on nest predation by mammals, birds, and snakes

    Science.gov (United States)

    W. Andrew Cox; F.R. Thompson III; J.L. Reidy

    2013-01-01

    Understanding how weather influences survival and reproduction is an important component of forecasting how climate change will influence wildlife population viability. Nest predation is the primary source of reproductive failure for passerine birds and can change in response to temperature. However, it is unclear which predator species are responsible for such...

  3. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment.

    Science.gov (United States)

    Ellison, Kevin S; Ribic, Christine A; Sample, David W; Fawcett, Megan J; Dadisman, John D

    2013-01-01

    Globally, grasslands and the wildlife that inhabit them are widely imperiled. Encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. In North America, most grassland birds avoid nesting near woody vegetation. Because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potential nest predators and the three most abundant grassland bird species (Henslow's sparrow [Ammodramus henslowii], Eastern meadowlark [Sturnella magna], and bobolink [Dolichonyx oryzivorus]) at sites in Wisconsin, U.S.A. We monitored 3 control and 3 treatment sites, for 1 yr prior to and 3 yr after tree row removal at the treatment sites. Grassland bird densities increased (2-4 times for bobolink and Henslow's sparrow) and nesting densities increased (all 3 species) in the removal areas compared to control areas. After removals, Henslow's sparrows nested within ≤50 m of the treatment area, where they did not occur when tree rows were present. Most dramatically, activity by woodland-associated predators nearly ceased (nine-fold decrease for raccoon [Procyon lotor]) at the removals and grassland predators increased (up to 27 times activity for thirteen-lined ground squirrel [Ictidomys tridecemlineatus]). Nest success did not increase, likely reflecting the increase in grassland predators. However, more nests were attempted by all 3 species (175 versus 116) and the number of successful nests for bobolinks and Henslow's sparrows increased. Because of gains in habitat, increased use by birds, greater production of young, and the effective removal of woodland-associated predators, tree row removal, where appropriate based on the predator community, can be a beneficial management action for conserving grassland birds and improving fragmented and degraded grassland ecosystems.

  4. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment.

    Directory of Open Access Journals (Sweden)

    Kevin S Ellison

    Full Text Available Globally, grasslands and the wildlife that inhabit them are widely imperiled. Encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. In North America, most grassland birds avoid nesting near woody vegetation. Because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potential nest predators and the three most abundant grassland bird species (Henslow's sparrow [Ammodramus henslowii], Eastern meadowlark [Sturnella magna], and bobolink [Dolichonyx oryzivorus] at sites in Wisconsin, U.S.A. We monitored 3 control and 3 treatment sites, for 1 yr prior to and 3 yr after tree row removal at the treatment sites. Grassland bird densities increased (2-4 times for bobolink and Henslow's sparrow and nesting densities increased (all 3 species in the removal areas compared to control areas. After removals, Henslow's sparrows nested within ≤50 m of the treatment area, where they did not occur when tree rows were present. Most dramatically, activity by woodland-associated predators nearly ceased (nine-fold decrease for raccoon [Procyon lotor] at the removals and grassland predators increased (up to 27 times activity for thirteen-lined ground squirrel [Ictidomys tridecemlineatus]. Nest success did not increase, likely reflecting the increase in grassland predators. However, more nests were attempted by all 3 species (175 versus 116 and the number of successful nests for bobolinks and Henslow's sparrows increased. Because of gains in habitat, increased use by birds, greater production of young, and the effective removal of woodland-associated predators, tree row removal, where appropriate based on the predator community, can be a beneficial management action for conserving grassland birds and improving fragmented and degraded grassland

  5. Habitat edges affect patterns of artificial nest predation along a wetland-meadow boundary

    Czech Academy of Sciences Publication Activity Database

    Suvorov, P.; Svobodová, J.; Albrecht, Tomáš

    2014-01-01

    Roč. 59, č. 1 (2014), s. 91-96 ISSN 1146-609X R&D Projects: GA ČR GA206/06/0851 Institutional support: RVO:68081766 Keywords : Artificial nest * Ecotonal effect * Habitat fragmentation * Nest predation * Wetland meadow Subject RIV: EG - Zoology Impact factor: 1.617, year: 2014

  6. Nest predation, clutch size, and physiological costs of egg production in the song sparrow (Melospiza melodia)

    OpenAIRE

    Travers, Marc Simon

    2009-01-01

    We examined the effects of nest predation on both clutch size and the physiological cost of egg production using a clutch removal experiment in free-living song sparrows (Melospiza melodia), inducing “high nest predation” (HNP) females to produce many replacement clutches compared to “low nest predation” (LNP) females. In a preliminary analysis we investigated the utility of multiple measures to assess “physiological condition”, including inter-correlations between physiological traits, sex d...

  7. Partitioning the sources of demographic variation reveals density-dependent nest predation in an island bird population.

    Science.gov (United States)

    Sofaer, Helen R; Sillett, T Scott; Langin, Kathryn M; Morrison, Scott A; Ghalambor, Cameron K

    2014-07-01

    Ecological factors often shape demography through multiple mechanisms, making it difficult to identify the sources of demographic variation. In particular, conspecific density can influence both the strength of competition and the predation rate, but density-dependent competition has received more attention, particularly among terrestrial vertebrates and in island populations. A better understanding of how both competition and predation contribute to density-dependent variation in fecundity can be gained by partitioning the effects of density on offspring number from its effects on reproductive failure, while also evaluating how biotic and abiotic factors jointly shape demography. We examined the effects of population density and precipitation on fecundity, nest survival, and adult survival in an insular population of orange-crowned warblers (Oreothlypis celata) that breeds at high densities and exhibits a suite of traits suggesting strong intraspecific competition. Breeding density had a negative influence on fecundity, but it acted by increasing the probability of reproductive failure through nest predation, rather than through competition, which was predicted to reduce the number of offspring produced by successful individuals. Our results demonstrate that density-dependent nest predation can underlie the relationship between population density and fecundity even in a high-density, insular population where intraspecific competition should be strong.

  8. Contrast in edge vegetation structure modifies the predation risk of natural ground nests in an agricultural landscape.

    Directory of Open Access Journals (Sweden)

    Nicole A Schneider

    Full Text Available Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe. As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation. No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland. This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i that edge effects depend on edge contrast, (ii that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk.

  9. Predator selection of prairie landscape features and its relation to duck nest success

    Science.gov (United States)

    Phillips, M.L.; Clark, W.R.; Sovada, M.A.; Horn, D.J.; Koford, Rolf R.; Greenwood, R.J.

    2003-01-01

    Mammalian predation is a major cause of mortality for breeding waterfowl in the U.S. Northern Great Plains, and yet we know little about the selection of prairie habitats by predators or how this influences nest success in grassland nesting cover. We selected 2 41.4-km2 study areas in both 1996 and 1997 in North Dakota, USA, with contrasting compositions of perennial grassland. A study area contained either 15-20% perennial grassland (Low Grassland Composition [LGC]) or 45-55% perennial grassland (High Grassland Composition [HGC]). We used radiotelemetry to investigate the selection of 9 landscape cover types by red fox (Vulpes vulpes) and striped skunk (Mephitis mephitis), while simultaneously recording duck nest success within planted cover. The cover types included the edge and core areas of planted cover, wetland edges within planted cover or surrounded by cropland, pastureland, hayland, cropland, roads, and miscellaneous cover types. Striped skunks selected wetland edges surrounded by agriculture over all other cover types in LGC landscapes (P-values for all pairwise comparisons were foraging efficiency in the interior areas of planted cover and contributed to higher nest success in HGC landscapes. Our observations of predator cover-type selection not only support the restoration and management of large blocks of grassland but also indicate the influence of alternative cover types for mitigating nest predation in the Prairie Pothole Region.

  10. Tupinambis merianae as nest predators of crocodilians and turtles in Florida, USA

    Science.gov (United States)

    Mazzotti, Frank J.; McEachern, Michelle A.; Rochford, Michael; Reed, Robert; Ketterlin Eckles, Jennifer; Vinci, Joy; Edwards, Jake; Wasilewki, Joseph

    2015-01-01

    Tupinambis merianae, is a large, omnivorous tegu lizard native to South America. Two populations of tegus are established in the state of Florida, USA, but impacts to native species are poorly documented. During summer 2013, we placed automated cameras overlooking one American alligator (Alligator mississippiensis) nest, which also contained a clutch of Florida red-bellied cooter (Pseudemys nelsoni) eggs, and one American crocodile (Crocodylus acutus) nest at a site in southeastern Florida where tegus are established. We documented tegu activity and predation on alligator and turtle eggs at the alligator nest, and tegu activity at the crocodile nest. Our finding that one of the first two crocodilian nests to be monitored was depredated by tegus suggests that tegus should be further evaluated as a threat to nesting reptiles in Florida.

  11. Facultative nest patch shifts in response to nest predation risk in the Brewer's sparrow: a "win-stay, lose-switch" strategy?

    Science.gov (United States)

    Anna D. Chalfoun; Thomas E. Martin

    2010-01-01

    Facultative shifts in nesting habitat selection in response to perceived predation risk may allow animals to increase the survival probability of sessile offspring. Previous studies on this behavioral strategy have primarily focused on single attributes, such as the distance moved or changes in nesting substrate. However, nest site choice often encompasses multiple...

  12. Predation drives nesting success in moist highland grasslands: the ...

    African Journals Online (AJOL)

    By focusing on process-oriented data rather than inventory-type data, this study provides a robust understanding of the effects of agricultural management on grassland bird reproductive output in the moist highland grasslands (MHGs) of South Africa. Four-hundred and four nests of 12 grassland-breeding bird species were ...

  13. Tests of landscape influence: nest predation and brood parasitism in fragmented ecosystems

    Science.gov (United States)

    Joshua J. Tewksbury; Lindy Garner; Shannon H. Garner; John D. Lloyd; Victoria A. Saab; Thomas E. Martin

    2006-01-01

    The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, we tracked...

  14. Vines and canopy contact: a route for snake predation on parrot nests.

    Science.gov (United States)

    SUSAN E. KOENIG; JOSEPH M. WUNDERLE; ERNESTO C. ENKERLINHOEFLICH

    2007-01-01

    Ornithologists have hypothesized that some tropical forest birds avoid snake predation by nesting in isolated trees that do not have vines and canopy contact with neighbouring trees. Here we review two complementary studies that support this hypothesis by demonstrating (1) that an abundance of vines and an interlocking canopy characterized Jamaican Black-billed Parrot...

  15. Breeding of Little Ringed Plovers Charadrius dubius in farmland: do nests in fields suffer from predation?

    Czech Academy of Sciences Publication Activity Database

    Cepáková, E.; Šálek, M.; Cepák, J.; Albrecht, Tomáš

    2007-01-01

    Roč. 54, č. 2 (2007), s. 284-288 ISSN 0006-3657 Institutional research plan: CEZ:AV0Z60930519 Keywords : Edge effect * Habitat fragmentation * Little Ringed Plover * Nest predation Subject RIV: EH - Ecology, Behaviour Impact factor: 0.880, year: 2007 http://www.ingentaconnect.com/content/bto/ bird /2007/00000054/00000002/art00019

  16. Factors determining pochard nest predation along a wetland gradient

    Czech Academy of Sciences Publication Activity Database

    Albrecht, Tomáš; Hořák, D.; Kreisinger, J.; Weidinger, K.; Klvaňa, P.; Michot, T. C.

    2006-01-01

    Roč. 70, č. 3 (2006), s. 784-791 ISSN 0022-541X Institutional research plan: CEZ:AV0Z60930519 Keywords : common pochard * artificial nests * edge effect Subject RIV: EG - Zoology Impact factor: 1.538, year: 2006 http://www.wildlifejournals.org/archive/0022-541X/70/3/pdf/i0022-541X-70-3-784.pdf

  17. Predation risk determines breeding territory choice in a Mediterranean cavity-nesting bird community.

    Science.gov (United States)

    Parejo, Deseada; Avilés, Jesús M

    2011-01-01

    Non-direct effects of predation can be an important component of the total effect of predation, modulating animal population and community dynamics. The isolated effects of predation risk on the spatial organisation of the breeding bird community, however, remains poorly studied. We investigated whether an experimentally increased predation risk prior to reproduction affected breeding territory selection and subsequent reproductive strategies in three Mediterranean cavity-nesting birds, i.e., the little owl Athene noctua, European roller Coracias garrulus and scops owl Otus scops. We found that territories used the previous year were more likely to be re-occupied when they belonged to the safe treatment rather than to the risky treatment. The first choice of breeders of all three species was for safe territories over risky ones. When all breeding attempts in the season (i.e., final occupation) were considered, breeders also preferred safe to risky sites. In addition, little owls laid larger eggs in risky territories than in safe territories. Our study provides experimental evidence of a rapid preventive response of the three most abundant species in a cavity-nesting bird community to a short-term manipulation of predation risk. This response highlights the key role of the non-direct effects of predation in modulating avian community organisation.

  18. Dynamics of habitat selection in birds: adaptive response to nest predation depends on multiple factors.

    Science.gov (United States)

    Devries, J H; Clark, R G; Armstrong, L M

    2018-05-01

    According to theory, habitat selection by organisms should reflect underlying habitat-specific fitness consequences and, in birds, reproductive success has a strong impact on population growth in many species. Understanding processes affecting habitat selection also is critically important for guiding conservation initiatives. Northern pintails (Anas acuta) are migratory, temperate-nesting birds that breed in greatest concentrations in the prairies of North America and their population remains below conservation goals. Habitat loss and changing land use practices may have decoupled formerly reliable fitness cues with respect to nest habitat choices. We used data from 62 waterfowl nesting study sites across prairie Canada (1997-2009) to examine nest survival, a primary fitness metric, at multiple scales, in combination with estimates of habitat selection (i.e., nests versus random points), to test for evidence of adaptive habitat choices. We used the same habitat covariates in both analyses. Pintail nest survival varied with nest initiation date, nest habitat, pintail breeding pair density, landscape composition and annual moisture. Selection of nesting habitat reflected patterns in nest survival in some cases, indicating adaptive selection, but strength of habitat selection varied seasonally and depended on population density and landscape composition. Adaptive selection was most evident late in the breeding season, at low breeding densities and in cropland-dominated landscapes. Strikingly, at high breeding density, habitat choice appears to become maladaptive relative to nest predation. At larger spatial scales, the relative availability of habitats with low versus high nest survival, and changing land use practices, may limit the reproductive potential of pintails.

  19. Density of the tegu lizard (Tupinambis merianae) and its role as nest predator at Anchieta Island, Brazil

    OpenAIRE

    Bovendorp, Ricardo S.; Alvarez, Ariane D.; Gialetti, Mauro

    2008-01-01

    Mammals has been pointed out to be the main nest predators in islands, but recent studies has shown that tree snakes are also important nest predator in tropical forests. Here we present information on the density tegu lizards Tupinambis merianae and its role as nest predator at Anchieta Island, Ubatuba, in southeastern Brazil. The mean density of tegu lizards wets estimated to be 83 individuals/km2, which is 1.83 times lower than other well-known population (Fernando de Noronha Archipelago)....

  20. Teste do efeito de borda na predação de ninhos naturais e artificiais no Cerrado A test of the edge effect on predation of natural and artificial bird nests in the Cerrado

    Directory of Open Access Journals (Sweden)

    Letice C. França

    2009-06-01

    Full Text Available The Cerrado is still one of the most important ecosystems in Brazil, even though more than 50% of its area has been altered or converted to pastureland and plantations. Despite its intense degradation, few ecological processes that might affect its biodiversity have been evaluated. The goal of this study was to test the edge effect on the predation rates at natural and artificial nests, at the Ecological Station of Águas Emendadas, Federal District, Brazil. Natural nests were found and monitored every three to four days from September to December of 2004 in the interior and at the edge of the reserve. Artificial nests were placed at four distances from the edge (0, 500, 1000 and 2000 m in three spatial replicates in September and again in December of 2004. Each nest received one Japanese Quail and one plasticine egg and was monitored every five days, for 15 days. There was no difference between the rates of predation either in the natural nests or in the artificial nests between treatments. For one bird species, Elaenia chiriquensis (Lawrence, 1865, Tyrannidae, daily survival rates in the incubation and in the hatchling period had opposite values between the edge and the interior. Marks on plasticine eggs suggest that birds are the main predators. Estimates of the abundance of two potential nest predators, Cyanocorax cristatellus (Temminck, 1823, Corvidae and Canis familiaris (Linnaeus, 1758, Canidae, revealed no relationship with distance to the edge, nor with predation rates. Brood parasitism of natural nests was similar between the interior (0% and the edge (3.8% of the nests. The results described here do not support the edge effect hypothesis for nest predation rates on either natural or artificial nests, nor for brood parasitism rates.

  1. Roads do not increase predation on experimental nests in a highly fragmented forest land

    Czech Academy of Sciences Publication Activity Database

    Svobodová, Jana; Šálek, M.; Albrecht, Tomáš

    2007-01-01

    Roč. 56, č. 1 (2007), s. 84-89 ISSN 0139-7893 R&D Projects: GA ČR GA206/01/1203 Institutional research plan: CEZ:AV0Z60930519 Keywords : artificial nest predation * black grouse * red fox Vulpes vulpes * travel line hypothesis Subject RIV: EH - Ecology, Behaviour Impact factor: 0.376, year: 2007 http://www.ivb.cz/folia/56/1/84-89_MS1260.pdf

  2. Predation in Ground-Nesting Birds: an Experimental Study Using Natural Egg-Color Variation

    Directory of Open Access Journals (Sweden)

    Aurora M. Castilla

    2007-06-01

    Full Text Available We tested the hypothesis that cryptically colored eggs would suffer less predation than conspicuous eggs in the ground-nesting red-legged partridge, Alectoris rufa. We used A. rufa as a model species because it has a wide range of natural egg colors, the eggs are widely available from breeding farms, and nests are easily mimicked because they are scrapes containing no vegetation. The study was conducted in the spring of 2001 in forest and fallow fields of central Spain in Castilla La Mancha, Ciudad Real. We used 384 clutches of natural eggs that were white, white spotted, brown, or brown spotted. Within clutches, eggs were consistent in color and size; among clutches, color differences were distributed across habitats. Clutches were checked once after 2 wk of exposure. Cryptic coloration had a survival advantage that was dependent on the local suite of predators. Rodent predation was nonselective with respect to clutch color; however, avian predation was significantly higher for conspicuous clutches. In addition, there was an interaction of landscape and egg color for avian predation. In forest landscapes, the clutches with highest survival were brown spotted, whereas in fallow landscapes, brown and brown spotted clutches had higher survival than white and white potted clutches. Thus, both the predator suite and the landscape had significant effects on the value of cryptic egg coloration. Our study is relevant for conservationists and managers in charge of restocking programs in hunting areas. The release of other partridge species or their hybrids could result in hybridization with wild partridges, potentially leading to nonoptimal clutch pigmentation and reduced survival of the native species. We therefore recommend that local authorities, managers, and conservationists be cautious with the use of alien species and hybrids and release only autochthonous species of partridges within their natural ranges.

  3. Predators

    Science.gov (United States)

    Young, Donald D.; McCabe, Thomas R.; Ambrose, Robert E.; Garner, Gerald W.; Weiler, Greg J.; Reynolds, Harry V.; Udevitz, Mark S.; Reed, Dan J.; Griffith, Brad; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Calving caribou (Rangifer tarandus) of the Central Arctic herd, Alaska, have avoided the infrastructure associated with the complex of petroleum development areas from Prudhoe Bay to Kuparuk (Cameron et al. 1992, Nellemann and Cameron 1998, and Section 4 of this document). Calving females of the Porcupine caribou herd may similarly avoid any oil field roads and pipelines developed in areas traditionally used during the calving and post-calving periods. This may displace the caribou females and calves to areas east and south of the 1002 Area of the Arctic National Wildlife Refuge.Increased calf mortality could occur if calving caribou are displaced into areas that have a higher density of predators, higher rates of predation, or where a higher proportion of the predators regularly use caribou as a food source (Whitten et al. 1992).Our study assessed predation risks to caribou calving in the 1002 Area versus calving in potential displacement areas. Due to funding constraints, our research focused on grizzly bears (Ursus arctos), with wolves (Camus lupus) and golden eagles (Aquila chrysaetos) receiving only cursory attention. Our research objectives were 1) to compare relative abundance of predators within the 1002 Area with that in adjacent peripheral areas, 2) to determine factors affecting predator abundance on the calving grounds, and 3) to quantify the use of caribou as a food source for predators and the importance of caribou to the productivity of predator populations using the coastal plain of the Arctic National Wildlife Refuge.

  4. Strike fast, strike hard: the red-throated caracara exploits absconding behavior of social wasps during nest predation.

    Science.gov (United States)

    McCann, Sean; Moeri, Onour; Jones, Tanya; Scott, Catherine; Khaskin, Grigori; Gries, Regine; O'Donnell, Sean; Gries, Gerhard

    2013-01-01

    Red-throated Caracaras Ibycter americanus (Falconidae) are specialist predators of social wasps in the Neotropics. It had been proposed that these caracaras possess chemical repellents that allow them to take the brood of wasp nests without being attacked by worker wasps. To determine how caracaras exploit nests of social wasps and whether chemical repellents facilitate predation, we: (1) video recorded the birds attacking wasp nests; (2) analyzed surface extracts of the birds' faces, feet, and feathers for potential chemical repellents; and (3) inflicted mechanical damage on wasp nests to determine the defensive behavior of wasps in response to varying levels of disturbance. During caracara predation events, two species of large-bodied wasps mounted stinging attacks on caracaras, whereas three smaller-bodied wasp species did not. The "hit-and-run" predation tactic of caracaras when they attacked nests of large and aggressive wasps reduced the risk of getting stung. Our data reveal that the predation strategy of caracaras is based on mechanical disturbance of, and damage to, target wasp nests. Caracara attacks and severe experimental disturbance of nests invariably caused wasps to abscond (abandon their nests). Two compounds in caracara foot extracts [sulcatone and iridodial] elicited electrophysiological responses from wasp antennae, and were also present in defensive secretions of sympatric arboreal-nesting Azteca ants. These compounds appear not to be wasp repellents but to be acquired coincidentally by caracaras when they perch on trees inhabited with Azteca ants. We conclude that caracara predation success does not depend on wasp repellents but relies on the absconding response that is typical of swarm-founding polistine wasps. Our study highlights the potential importance of vertebrate predators in the ecology and evolution of social wasps.

  5. Increasing nest predation will be insufficient to maintain polar bear body condition in the face of sea ice loss.

    Science.gov (United States)

    Dey, Cody J; Richardson, Evan; McGeachy, David; Iverson, Samuel A; Gilchrist, Hugh G; Semeniuk, Christina A D

    2017-05-01

    Climate change can influence interspecific interactions by differentially affecting species-specific phenology. In seasonal ice environments, there is evidence that polar bear predation of Arctic bird eggs is increasing because of earlier sea ice breakup, which forces polar bears into nearshore terrestrial environments where Arctic birds are nesting. Because polar bears can consume a large number of nests before becoming satiated, and because they can swim between island colonies, they could have dramatic influences on seabird and sea duck reproductive success. However, it is unclear whether nest foraging can provide an energetic benefit to polar bear populations, especially given the capacity of bird populations to redistribute in response to increasing predation pressure. In this study, we develop a spatially explicit agent-based model of the predator-prey relationship between polar bears and common eiders, a common and culturally important bird species for northern peoples. Our model is composed of two types of agents (polar bear agents and common eider hen agents) whose movements and decision heuristics are based on species-specific bioenergetic and behavioral ecological principles, and are influenced by historical and extrapolated sea ice conditions. Our model reproduces empirical findings that polar bear predation of bird nests is increasing and predicts an accelerating relationship between advancing ice breakup dates and the number of nests depredated. Despite increases in nest predation, our model predicts that polar bear body condition during the ice-free period will continue to decline. Finally, our model predicts that common eider nests will become more dispersed and will move closer to the mainland in response to increasing predation, possibly increasing their exposure to land-based predators and influencing the livelihood of local people that collect eider eggs and down. These results show that predator-prey interactions can have nonlinear responses to

  6. Predator protection or similar habitat selection in red-breasted goose nesting associations : extremes along a continuum

    NARCIS (Netherlands)

    Quinn, JL; Prop, J; Kokorev, Y; Black, JM

    We tested the predator protection and similar habitat hypotheses in relation to red-breasted goose, Branta ruficollis, nesting associations. Geese began laying 1-3 weeks after all associated species. In almost all cases they nested on the mainland only if raptors were also present and always

  7. Daily survival rates for nests of Black Skimmers from a core breeding area of the Southeastern USA

    Science.gov (United States)

    Brooks, Gillian L.; Sanders, Felicia J.; Gerard, Patrick D.; Jodice, Patrick G.R.

    2014-01-01

    Little is known about the reproductive success of Black Skimmers (Rynchops niger) throughout the southeastern USA where availability of undisturbed beaches for nesting is limited. Daily survival rates (DSR) of nests were examined at three nesting sites in Cape Romain National Wildlife Refuge (CRNWR), South Carolina, USA, 2009–2010. The percent of successful nests (n  =  346 nests) ranged from 42–69% among colony sites when data were pooled across both years. The DSR of nests was primarily related to colony site, predation risk, height of high tide, and clutch size. Predation and overwash were the principal causes of identifiable nest loss, each accounting for ∼33% of nest failures during the two study years. Because of the challenges of resighting skimmer chicks, we were not able to measure chick survival effectively and therefore accurate measures of productivity remain elusive. High variability in nest success among sites within close proximity to each other (stressors such as tropical storms or food availability. Although time-intensive techniques to control predators do exist, management options to limit flooding and overwash are far more limited. Conservation of Black Skimmers in the southeastern USA would benefit from coordinated, multi-state efforts to measure nest and chick survival.

  8. Predation rate by wolves on the Porcupine caribou herd

    OpenAIRE

    Hayes, Robert D.; Russell, Donald E.

    2000-01-01

    Large migratory catibou {Rangifer tarandus) herds in the Arctic tend to be cyclic, and population trends are mainly driven by changes in forage or weather events, not by predation. We estimated daily kill rate by wolves on adult caribou in winter, then constructed a time and space dependent model to estimate annual wolf (Canis lupus) predation rate (P annual) on adult Porcupine caribou. Our model adjusts predation seasonally depending on caribou distribution: Pannual = SIGMAdaily* W *Ap(2)*Dp...

  9. Daily survival rate and habitat characteristics of nests of Wilson's Plover

    Science.gov (United States)

    Zinsser, Elizabeth; Sanders, Felicia J.; Gerard, Patrick D.; Jodice, Patrick G.R.

    2017-01-01

    We assessed habitat characteristics and measured daily survival rate of 72 nests of Charadrius wilsonia (Wilson's Plover) during 2012 and 2013 on South Island and Sand Island on the central coast of South Carolina. At both study areas, nest sites were located at slightly higher elevations (i.e., small platforms of sand) relative to randomly selected nearby unused sites, and nests at each study area also appeared to be situated to enhance crypsis and/or vigilance. Daily survival rate (DSR) of nests ranged from 0.969 to 0.988 among study sites and years, and the probability of nest survival ranged from 0.405 to 0.764. Flooding and predation were the most common causes of nest failure at both sites. At South Island, DSR was most strongly related to maximum tide height, which suggests that flooding and overwash may be common causes of nest loss for Wilson's Plovers at these study sites. The difference in model results between the 2 nearby study sites may be partially due to more-frequent flooding at Sand Island because of some underlying yet unmeasured physiographic feature. Remaining data gaps for the species include regional assessments of nest and chick survival and habitat requirements during chick rearing.

  10. Habitat characteristics of nesting areas and of predated nests in a Mediterranean population of the European pond turtle, Emys orbicularis galloitalica

    Directory of Open Access Journals (Sweden)

    Marco A.L. Zuffi

    2006-01-01

    Full Text Available one of the largest population of Emys orbicularis galloitalica of central Italy inhabits the canal system wet areas within a natural protected park. Features of nesting habitats, nest structure, and predation patterns of 209 nests of a large population of the European pond turtle are here presented and analysed. Nest sites were characterised by sunny bushy areas in strip habitat, digged along north-south oriented canals, on average with about 26% of the area covered by vegetation, less than one meter distant from 30 cm height bushes, at about 11 m from water and at about 13 m distance from wooded areas, 28 m away from a road. Principal Component and discriminant analyses were used on 20 selected variables in order to reduce the number of physical variables, and indicate that canal border, strip habitat, and canal orientation are grouping variables, that correctly classified 41.6%, 66.5%, and 100 % respectively of nest presence.

  11. Local density regulates migratory songbird reproductive success through effects on double-brooding and nest predation.

    Science.gov (United States)

    Woodworth, Bradley K; Wheelwright, Nathaniel T; Newman, Amy E M; Norris, D Ryan

    2017-08-01

    Knowledge of the density-dependent processes that regulate animal populations is key to understanding, predicting, and conserving populations. In migratory birds, density-dependence is most often studied during the breeding season, yet we still lack a robust understanding of the reproductive traits through which density influences individual reproductive success. We used 27-yr of detailed, individual-level productivity data from an island-breeding population of Savannah sparrows Passerculus sandwichensis to evaluate effects of local and total annual population density on female reproductive success. Local density (number of neighbors within 50 m of a female's nest) had stronger effects on the number of young fledged than did total annual population density. Females nesting in areas of high local density were more likely to suffer nest predation and less likely to initiate and fledge a second clutch, which led to fewer young fledged in a season. Fledging fewer young subsequently decreased the likelihood of a female recruiting offspring into the breeding population in a subsequent year. Collectively, these results provide insight into the scale and reproductive mechanisms mediating density-dependent reproductive success and fitness in songbirds. © 2017 by the Ecological Society of America.

  12. Evolution of avian clutch size along latitudinal gradients: do seasonality, nest predation or breeding season length matter?

    Science.gov (United States)

    Griebeler, E M; Caprano, T; Böhning-Gaese, K

    2010-05-01

    Birds display a latitudinal gradient in clutch size with smaller clutches in the tropics and larger in the temperate region. Three factors have been proposed to affect this pattern: seasonality of resources (SR), nest predation and length of the breeding season (LBS). Here, we test the importance of these factors by modelling clutch size evolution within bird populations under different environmental settings. We use an individual-based ecogenetic simulation model that combines principles from population ecology and life history theory. Results suggest that increasing SR from the tropics to the poles by itself or in combination with a decreasing predation rate and LBS can generate the latitudinal gradient in clutch size. Annual fecundity increases and annual adult survival rate decreases from the tropics to the poles. We further show that the annual number of breeding attempts that (together with clutch size) determines total annual egg production is an important trait to understand latitudinal patterns in these life history characteristics. Field experiments that manipulate environmental factors have to record effects not only on clutch size, but also on annual number of breeding attempts. We use our model to predict the outcome of such experiments under different environmental settings.

  13. Predation rates, timing, and predator composition for Scoters (Melanitta spp.) in marine habitats

    Science.gov (United States)

    Anderson, Eric J.; Esler, Daniel N.; Sean, Boyd W.; Evenson, Joseph; Nysewander, David R.; Ward, David H.; Dickson, Rian D.; Uher-Koch, Brian D.; Vanstratt, C.S.; Hupp, Jerry

    2012-01-01

    Studies of declining populations of sea ducks have focused mainly on bottom-up processes with little emphasis on the role of predation. We identified 11 potential predators of White-winged Scoters (Melanitta fusca (L., 1758)) and Surf Scoters (Melanitta perspicillata (L., 1758)) in North American marine habitats. However, of 596 Scoters marked with VHF transmitters along the Pacific coast, mortalities were recovered in association with just two identifiable categories of predators: in southeast Alaska recoveries occurred mainly near mustelid feeding areas, while those in southern British Columbia and Washington occurred mainly near feeding areas of Bald Eagles (Haliaeetus leucocephalus (L., 1766)). Determining whether marked Scoters had been depredated versus scavenged was often not possible, but mortalities occurred more frequently during winter than during wing molt (13.1% versus 0.7% of both species combined, excluding Scoters that died within a postrelease adjustment period). In two sites heavily used by Scoters, diurnal observations revealed no predation attempts and low rates of predator disturbances that altered Scoter behavior (≤ 0.22/h). These and other results suggest that predation by Bald Eagles occurs mainly at sites and times where densities of Scoters are low, while most predation by mustelids probably occurs when Scoters are energetically compromised.

  14. Predação de ninhos de Trachemys dorbigni (Duméril & Bibron (Testudines, Emydidae no extremo sul do Brasil Nest predation of Trachemys dorbigni (Duméril & Bibron (Testudines, Emydidae in Southern Brazil

    Directory of Open Access Journals (Sweden)

    Fernanda A. Gonçalves

    2007-12-01

    Full Text Available Ninhos da tartaruga tigre-d'água, Trachemys dorbigni, foram monitorados durante a estação reprodutiva de 2005/2006 para avaliar as taxas de predação e a variação temporal destas; identificar as espécies predadoras, sua importância na destruição dos ninhos e determinar a influência da dispersão dos ninhos sobre a predação, no extremo sul do Brasil. Dos 58 ninhos monitorados, 98% (n = 57 foram destruídos por predadores. Eventos de predação ocorreram predominantemente nas primeiras 48 horas após a oviposição e não houve variação temporal nas taxas de predação. Através de armadilhas fotográficas e observações diretas foram identificadas seis espécies predadoras dos ninhos, não havendo prevalência de nenhuma das espécies. A densidade de ninhos não influenciou as taxas de predação, mas houve correlação negativa entre densidade e tempo decorrido entre a desova e a predação.Nests of the D'Orbigny's slider, Trachemys dorbigni, were monitored during the nesting season of 2005/2006 to evaluate predation rates; time variation on these rates; to identify predator species and their importance on nest destruction and the influence of nest dispersion on predation rates in Southern Brazil. Of the 58 monitored nests, 98% (n = 57 were destroyed by predators. Predation events occurred primarily during the first 48 hours after oviposition and there was no time variation on predation rates. Using camera traps and direct observations we could identify six species of nest predators. There was not prevalence of any predator. Nest density did not influence predation rates, but there was a negative correlation between time after egg laying and predation.

  15. Nest Mosquito Trap quantifies contact rates between nesting birds and mosquitoes.

    Science.gov (United States)

    Caillouët, Kevin A; Riggan, Anna E; Rider, Mark; Bulluck, Lesley P

    2012-06-01

    Accurate estimates of host-vector contact rates are required for precise determination of arbovirus transmission intensity. We designed and tested a novel mosquito collection device, the Nest Mosquito Trap (NMT), to collect mosquitoes as they attempt to feed on unrestrained nesting birds in artificial nest boxes. In the laboratory, the NMT collected nearly one-third of the mosquitoes introduced to the nest boxes. We then used these laboratory data to estimate our capture efficiency of field-collected bird-seeking mosquitoes collected over 66 trap nights. We estimated that 7.5 mosquitoes per trap night attempted to feed on nesting birds in artificial nest boxes. Presence of the NMT did not have a negative effect on avian nest success when compared to occupied nest boxes that were not sampled with the trap. Future studies using the NMT may elucidate the role of nestlings in arbovirus transmission and further refine estimates of nesting bird and vector contact rates. © 2012 The Society for Vector Ecology.

  16. Predicting prey population dynamics from kill rate, predation rate and predator-prey ratios in three wolf-ungulate systems.

    Science.gov (United States)

    Vucetich, John A; Hebblewhite, Mark; Smith, Douglas W; Peterson, Rolf O

    2011-11-01

    1. Predation rate (PR) and kill rate are both fundamental statistics for understanding predation. However, relatively little is known about how these statistics relate to one another and how they relate to prey population dynamics. We assess these relationships across three systems where wolf-prey dynamics have been observed for 41 years (Isle Royale), 19 years (Banff) and 12 years (Yellowstone). 2. To provide context for this empirical assessment, we developed theoretical predictions of the relationship between kill rate and PR under a broad range of predator-prey models including predator-dependent, ratio-dependent and Lotka-Volterra dynamics. 3. The theoretical predictions indicate that kill rate can be related to PR in a variety of diverse ways (e.g. positive, negative, unrelated) that depend on the nature of predator-prey dynamics (e.g. structure of the functional response). These simulations also suggested that the ratio of predator-to-prey is a good predictor of prey growth rate. That result motivated us to assess the empirical relationship between the ratio and prey growth rate for each of the three study sites. 4. The empirical relationships indicate that PR is not well predicted by kill rate, but is better predicted by the ratio of predator-to-prey. Kill rate is also a poor predictor of prey growth rate. However, PR and ratio of predator-to-prey each explained significant portions of variation in prey growth rate for two of the three study sites. 5. Our analyses offer two general insights. First, Isle Royale, Banff and Yellowstone are similar insomuch as they all include wolves preying on large ungulates. However, they also differ in species diversity of predator and prey communities, exploitation by humans and the role of dispersal. Even with the benefit of our analysis, it remains difficult to judge whether to be more impressed by the similarities or differences. This difficulty nicely illustrates a fundamental property of ecological

  17. Using DNA from hairs left at depredated greater sage-grouse nests to detect mammalian nest predators

    Science.gov (United States)

    Christopher P. Kirol; Kristine L. Pilgrim; Andrew L. Sutphin; Thomas L. Maechtle

    2018-01-01

    Despite a multitude of studies on sage-grouse (Centrocercus spp.), there is still sparse information on the predator communities that influence sage-grouse productivity and how these predator communities may change when sagebrush habitats are altered by human activities. As a proof-of-concept, we used mammalian hairs collected at depredated greater sage-grouse (C....

  18. Molecular forensics in avian conservation: a DNA-based approach for identifying mammalian predators of ground-nesting birds and eggs.

    Science.gov (United States)

    Hopken, Matthew W; Orning, Elizabeth K; Young, Julie K; Piaggio, Antoinette J

    2016-01-07

    The greater sage-grouse (Centrocercus urophasianus) is a ground-nesting bird from the Northern Rocky Mountains and a species at risk of extinction in in multiple U.S. states and Canada. Herein we report results from a proof of concept that mitochondrial and nuclear DNAs from mammalian predator saliva could be non-invasively collected from depredated greater sage-grouse eggshells and carcasses and used for predator species identification. Molecular forensic approaches have been applied to identify predators from depredated remains as one strategy to better understand predator-prey dynamics and guide management strategies. This can aid conservation efforts by correctly identifying predators most likely to impact threatened and endangered species. DNA isolated from non-invasive samples around nesting sites (e.g. fecal or hair samples) is one method that can increase the success and accuracy of predator species identification when compared to relying on nest remains alone. Predator saliva DNA was collected from depredated eggshells and carcasses using swabs. We sequenced two partial fragments of two mitochondrial genes and obtained microsatellite genotypes using canid specific primers for species and individual identification, respectively. Using this multilocus approach we were able to identify predators, at least down to family, from 11 out of 14 nests (79%) and three out of seven carcasses (47%). Predators detected most frequently were canids (86%), while other taxa included rodents, a striped skunk, and cattle. We attempted to match the genotypes of individual coyotes obtained from eggshells and carcasses with those obtained from fecal samples and coyotes collected in the areas, but no genotype matches were found. Predation is a main cause of nest failure in ground-nesting birds and can impact reproduction and recruitment. To inform predator management for ground-nesting bird conservation, accurate identification of predator species is necessary. Considering

  19. Predation rate by wolves on the Porcupine caribou herd

    Directory of Open Access Journals (Sweden)

    Robert D. Hayes

    2000-04-01

    Full Text Available Large migratory catibou {Rangifer tarandus herds in the Arctic tend to be cyclic, and population trends are mainly driven by changes in forage or weather events, not by predation. We estimated daily kill rate by wolves on adult caribou in winter, then constructed a time and space dependent model to estimate annual wolf (Canis lupus predation rate (P annual on adult Porcupine caribou. Our model adjusts predation seasonally depending on caribou distribution: Pannual = SIGMAdaily* W *Ap(2*Dp. In our model we assumed that wolves killed adult caribou at a constant rate (Kdaily, 0.08 caribou wolf1 day1 based on our studies and elsewhere; that wolf density (W doubled to 6 wolves 1000 km2-1 on all seasonal ranges; and that the average area occupied by the Porcupine caribou herd (PCH in eight seasonal life cycle periods (Dp was two times gteater than the area described by the outer boundaries of telemetry data (Ap /1000 km2. Results from our model projected that wolves kill about 7600 adult caribou each year, regardless of herd size. The model estimated that wolves removed 5.8 to 7.4% of adult caribou as the herd declined in the 1990s. Our predation rate model supports the hypothesis of Bergerud that spacing away by caribou is an effective anti-predatory strategy that greatly reduces wolf predation on adult caribou in the spring and summer.

  20. Nesting success and survival rates of suburban Olive Thrushes ...

    African Journals Online (AJOL)

    Reproductive rate, clutch size, nesting success and survival rate of dependent fledglings were estimated from breeding records in the Eastern Cape. These data were used to estimate survival rate of independent fledglings. The estimated adult survival rate in this region was high and the clutch size was small, compared to ...

  1. The role of fragmentation and landscape changes in the ecological release of common nest predators in the Neotropics

    Directory of Open Access Journals (Sweden)

    Michael V. Cove

    2014-07-01

    Full Text Available Loss of large mammalian carnivores may allow smaller mesopredators to become abundant and threaten other community members. There is considerable debate about mesopredator release and the role that other potential factors such as landscape variables and human alterations to land cover lead to increased mesopredator abundance. We used camera traps to detect four mesopredators (tayra, Eira barbara; white-nosed coati, Nasua narica; northern raccoon, Procyon lotor; and common opossum, Didelphis opossum in a biological corridor in Costa Rica to estimate habitat covariates that influenced the species’ detection and occurrence. We selected these mesopredators because as semi-arboreal species they might be common nest predators, posing a serious threat to resident and migratory songbirds. Pineapple production had a pronounced positive effect on the detectability of tayras, while forest cover had a negative effect on the detection of coatis. This suggests that abundance might be elevated due to the availability of agricultural food resources and foraging activities are concentrated in forest fragments and pineapple edge habitats. Raccoon and opossum models exhibited little influence on detection from habitat covariates. Occurrence models did not suggest any significant factors influencing site use by nest predators, revealing that all four species are habitat generalists adapted to co-existing in human altered landscapes. Furthermore, fragmentation and land cover changes may predispose nesting birds, herpetofauna, and small mammals to heightened predation risk by mesopredators in the Neotropics.

  2. Reconciling actual and perceived rates of predation by domestic cats

    Science.gov (United States)

    McDonald, Jennifer L; Maclean, Mairead; Evans, Matthew R; Hodgson, Dave J

    2015-01-01

    The predation of wildlife by domestic cats (Felis catus) is a complex problem: Cats are popular companion animals in modern society but are also acknowledged predators of birds, herpetofauna, invertebrates, and small mammals. A comprehensive understanding of this conservation issue demands an understanding of both the ecological consequence of owning a domestic cat and the attitudes of cat owners. Here, we determine whether cat owners are aware of the predatory behavior of their cats, using data collected from 86 cats in two UK villages. We examine whether the amount of prey their cat returns influences the attitudes of 45 cat owners toward the broader issue of domestic cat predation. We also contribute to the wider understanding of physiological, spatial, and behavioral drivers of prey returns among cats. We find an association between actual prey returns and owner predictions at the coarse scale of predatory/nonpredatory behavior, but no correlation between the observed and predicted prey-return rates among predatory cats. Cat owners generally disagreed with the statement that cats are harmful to wildlife, and disfavored all mitigation options apart from neutering. These attitudes were uncorrelated with the predatory behavior of their cats. Cat owners failed to perceive the magnitude of their cats’ impacts on wildlife and were not influenced by ecological information. Management options for the mitigation of cat predation appear unlikely to work if they focus on “predation awareness” campaigns or restrictions of cat freedom. PMID:26306163

  3. Reproductive Consequences of Nest Site Use in Fork-tailed Storm-Petrels in the Aleutian Islands, Alaska: Potential Lasting Effects of an Introduced Predator

    Directory of Open Access Journals (Sweden)

    Brie A. Drummond

    2010-12-01

    Full Text Available We examined the reproductive consequences of differential nest site use in Fork-tailed Storm-Petrels (Oceanodroma furcata in the Aleutian Islands, Alaska, where birds on islands where foxes were introduced nest in rocky substrate rather than in typical soil habitat. We investigated how physical and microclimatic nest site characteristics influenced storm-petrel breeding success 20 years after fox removal. We then examined whether those nest site characteristics that affected success were related to the amount of rock that composed the nest. In both years of our study, nest temperature had the strongest influence on chick survival and overall reproductive success, appearing in all the top models and alone explaining 14-35% of the variation in chick survival. The relationship between reproductive success and nest temperature was positive in both years, with higher survival in warmer nests. In turn, the best predictor of nest temperature was the amount of rock that composed the site. Rockier nests had colder average temperatures, which were driven by lower daily minimum temperatures, compared to nests with more soil. Thus, the rockiness of the nest site appeared to affect chick survival and overall reproductive success through its influence on nest temperature. This study suggests that the use of rocky nest sites, presumed to be a result of historic predation from introduced foxes, could decrease breeding success in this recovering population, and thus be a long-lasting effect of introduced predators.

  4. Nesting bird "host funnel" increases mosquito-bird contact rate.

    Science.gov (United States)

    Caillouët, Kevin A; Riggan, Anna E; Bulluck, Lesley P; Carlson, John C; Sabo, Roy T

    2013-03-01

    Increases in vector-host contact rates can enhance arbovirus transmission intensity. We investigated weekly fluctuations in contact rates between mosquitoes and nesting birds using the recently described Nest Mosquito Trap (NMT). The number of mosquitoes per nestling increased from nesting season. Our evidence suggests the coincidence of the end of the avian nesting season and increasing mosquito abundances may have caused a "host funnel," concentrating host-seeking mosquitoes to the few remaining nestlings. The relative abundance of mosquitoes collected by the NMT suggests that significantly more Aedes albopictus (Skuse) and Culex pipiens (L.) /restuans (Theobald) sought nesting bird bloodmeals than were predicted by their relative abundances in CO2-baited Centers for Disease Control and Prevention light and gravid traps. Culex salinarius (Coquillett) and Culex erraticus Dyar and Knab were collected in NMTs in proportion to their relative abundances in the generic traps. Temporal host funnels and nesting bird host specificity may enhance arbovirus amplification and explain observed West Nile virus and St. Louis encephalitis virus amplification periods.

  5. Breeding in a den of thieves : Pros and cons of nesting close to egg predators

    NARCIS (Netherlands)

    de Fouw, Jimmy; Bom, Roeland A.; Klaassen, Raymond H. G.; Muskens, Gerard J. D. M.; de Vries, Peter P.; Popov, Igor Yu.; Kokorev, Yakov I.; Ebbinge, Barwolt S.; Nolet, Bart A.

    Breeding success of many Arctic-breeding bird populations varies with lemming cycles due to prey switching behavior of generalist predators. Several bird species breed on islands to escape from generalist predators like Arctic fox Vulpes lagopus, but little is known about how these species interact.

  6. Breeding in a den of thieves: pros and cons of nesting close to egg predators

    NARCIS (Netherlands)

    de Fouw, J; Bom, R.A.; Klaassen, R.H.G.; Müskens, G.J. D. M.; de Vries, P.P.; Popov, I.Y.; Kokorev, Y.I.; Ebbinge, B.S.; Nolet, B.A.

    2016-01-01

    Breeding success of many Arctic-breedingbird populations varies with lemming cycles dueto prey switching behavior of generalist predators. Several bird species breed on islands to escape fromgeneralist predators like Arctic fox Vulpes lagopus, but little is known about how these species interact.We

  7. Breeding in a den of thieves: pros and cons of nesting close to egg predators

    NARCIS (Netherlands)

    de Fouw, J.; Bom, R.A.; Klaassen, R.H.G.; Müskens, G.J.D.M.; de Vries, P.P.; Popov, I.Yu.; Kokorev, Y.I.; Ebbinge, B.S.; Nolet, B.A.

    Breeding success of many Arctic-breeding bird populations varies with lemming cycles due to prey switching behavior of generalist predators. Several bird species breed on islands to escape from generalist predators like Arctic fox Vulpes lagopus, but little is known about how these species interact.

  8. Breeding in a den of thieves: pros and cons of nesting close to egg predators.

    NARCIS (Netherlands)

    De Fouw, J.; Bom, R. A.; Klaassen, R.; Müskens, G.J.D.M.; De Vries, P.P.; Popov, I.Y.; Kokorev, Y.I.; Ebbinge, B.S.; Nolet, B.A.

    2016-01-01

    Breeding success of many Arctic-breeding bird populations varies with lemming cycles due to prey switching behavior of generalist predators. Several bird species breed on islands to escape from generalist predators like Arctic fox Vulpes lagopus, but little is known about how these species interact.

  9. Drought-caused delay in nesting of Sonoran Desert birds and its facilitation of parasite- and predator-mediated variation in reproductive success

    Science.gov (United States)

    McCreedy, Chris; van Riper, Charles

    2015-01-01

    As our understanding of climate change has increased, so has our awareness of the impacts of these changes on biotic systems. Climate models are nearly unanimous in their predictions for increased drought frequency in southwestern North America, and delays in nest initiation due to drought may influence nesting success and productivity for many Sonoran Desert bird species. In southeastern California and western Arizona in 2004–2009, we found negative correlations for 13 of 13 species between nest initiation date and rainfall accumulation during the preceding 4-month winter rainy season. Nesting was delayed more than 3 weeks for some species during extreme droughts in 2006 and 2007. During 2004–2009, we found a significant negative effect of nest initiation date on nest survival probability (β̂ = −0.031 ± 0.005 SE, P nesting delay in nesting success and productivity, in 2010 we conducted a manipulative experiment with Black-tailed Gnatcatchers (Polioptila melanura; BTGN) and Verdins (Auriparus flaviceps; VERD). Following a wet winter, we delayed clutch initiation dates for treatment pairs to match first-egg dates that we observed during droughts in 2006 and 2007. Nest initiation date had a significant negative effect on nest survival of both species (BTGN: β̂ = −1.18 ± 0.27 SE, P nest predation and Brown-headed Cowbird (Molothrus ater) parasitism were the most common causes of nest failure, we conclude that the impacts of climate change–caused drought on annual reproductive output in the Sonoran Desert will be further compounded by parasitism and predation for Black-tailed Gnatcatchers and by predation for Verdins.

  10. Grizzly bear predation rates on caribou calves in northeastern Alaska

    Science.gov (United States)

    Young, Donald D.; McCabe, Thomas R.

    1997-01-01

    During June 1993 and 1994, 11 radiocollared and 7 unmarked grizzly bears (Ursus arctos) were monitored visually (observation) from fixed-wing aircraft to document predation on calves of the Porcupine Caribou (Rangifer tarandus) Herd (PCH) in northeastern Alaska. Twenty-six (72%) grizzly bear observations were completed (???60 min) successfully (median duration = 180 min; ??95% CI = 136-181 min; range = 67-189 min) and 10 were discontinued (duration ???24 min) due to disturbance to the bear, or unfavorable weather conditions. Of the 26 successfully completed observations, 15 (58%) included predatory activity (encounter) directed at caribou calves and 8 (31%) included kills. Of 32 encounters, 9 resulted in kills, for a success rate of 28%. The median duration of encounters was 1 minute (??95% CI = 1-2 min; range = 1-6 min; n = 32;), and the median time spent at a kill was 14 minutes (??95% CI = 9-23 min; range = 6-56 min; n = 9). Sows with young (n = 4) killed more frequently (75%; P = 0.0178) than barren sows, boars, and consorting pairs combined (17%; n = 18). Estimated kill rate was highest for sows with young (6.3 kills/bear/day; n = 4), followed by barren sows (4.6 kills/bear/day; n = 5), boars (1.9 kills/bear/day; n = 5), and, finally, consorting pairs (1.0 kills/bear/day; n = 8). Estimated kill rate obtained via conventional radiotracking point surveys (4.8 kills/bear/day) was higher than that obtained via concurrent bear observations (3.1 kills/bear/day). Our research provides baseline estimates of predation rates by grizzly bears on caribou calves that will enhance the capability of wildlife professionals in managing populations of both predators and their prey.

  11. Do artificial nests simulate nest success of greater sage-grouse?

    OpenAIRE

    Dinkins, Jonathan B.; Conover, Michael R.; Mabray, Scott T.

    2013-01-01

    Artificial nests have been used to study factors affecting nest success because researchers can manipulate them more than natural bird nests. Many researchers have questioned the validity of generalizing the results from artificial nests onto naturally occurring nests. Other studies have assessed the validity of artificial nest studies by simultaneously comparing overall depredation or daily survival rates, depredation timing, predator species, or habitat characteristics of artificial and nat...

  12. Factors influencing the predation rates of Anisops breddini (Hemiptera: Notonectidae feeding on mosquito larvae

    Directory of Open Access Journals (Sweden)

    R. Weterings

    2014-12-01

    Full Text Available Notonectidae are a family of water bugs that are known to be important predators of mosquito larvae and have great potential in the biological control of vector mosquitoes. An experiment was conducted to assess mosquito larvae predation by Anisops breddini, a species common to Southeast Asia. The predation rates were recorded in context of prey density, predator density, predator size and prey type. Predation rates were strongly affected by prey type and less by prey density and predator density. They ranged between 1.2 prey items per day for pupae of Aedes aegeypti and Armigeres moultoni to 5.9 for Ae. aegypti larvae. Compared with studies on other Notonectidae species, the predation rates appear low, which is probably caused by the relative small size of the specimens used in this study. An. breddini is very common in the region and often found in urban areas; therefore, the species has potential as a biological control agent.

  13. Seasonal and among-stream variation in predator encounter rates for fish prey

    Science.gov (United States)

    Bret C. Harvey; Rodney J. Nakamoto

    2013-01-01

    Recognition that predators have indirect effects on prey populations that may exceed their direct consumptive effects highlights the need for a better understanding of spatiotemporal variation in predator–prey interactions. We used photographic monitoring of tethered Rainbow Trout Oncorhynchus mykiss and Cutthroat Trout O. clarkii to quantify predator encounter rates...

  14. The influence of nestling predation on nest site sele,ction and ...

    African Journals Online (AJOL)

    1987-08-25

    Aug 25, 1987 ... every tree taller than 6 m was recorded for trees within a. 100-m radius of the nest tree. The angular dispersion of ... the mean angular deviation, S (Zar 1984). S can vary ..... Further research in which the number and quality of.

  15. Do common cuckoo chicks suffer nest predation more than host nestlings?

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Václav; Karasová, Tereza; Weidinger, K.; Procházka, Petr; Honza, Marcel

    2016-01-01

    Roč. 70, č. 11 (2016), s. 1975-1987 ISSN 0340-5443 R&D Projects: GA ČR(CZ) GAP506/12/2404 Institutional support: RVO:68081766 Keywords : Brood parasitism * Great reed warbler * Nest survival * Reed warbler Subject RIV: EG - Zoology Impact factor: 2.185, year: 2016

  16. Experimental enlargement of nest size does not increase risk of predation or brood parasitism in the Great Reed Warbler Acrocephalus arundinaceus

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Václav; Procházka, Petr; Honza, Marcel

    2015-01-01

    Roč. 157, č. 2 (2015), s. 396-400 ISSN 0019-1019 R&D Projects: GA AV ČR IAA600930903; GA ČR(CZ) GAP506/12/2404 Institutional support: RVO:68081766 Keywords : Common Cuckoo * nest survival * predation Subject RIV: EG - Zoology Impact factor: 1.804, year: 2015

  17. Inferring predator behavior from attack rates on prey-replicas that differ in conspicuousness.

    Directory of Open Access Journals (Sweden)

    Yoel E Stuart

    Full Text Available Behavioral ecologists and evolutionary biologists have long studied how predators respond to prey items novel in color and pattern. Because a predatory response is influenced by both the predator's ability to detect the prey and a post-detection behavioral response, variation among prey types in conspicuousness may confound inference about post-prey-detection predator behavior. That is, a relatively high attack rate on a given prey type may result primarily from enhanced conspicuousness and not predators' direct preference for that prey. Few studies, however, account for such variation in conspicuousness. In a field experiment, we measured predation rates on clay replicas of two aposematic forms of the poison dart frog Dendrobates pumilio, one novel and one familiar, and two cryptic controls. To ask whether predators prefer or avoid a novel aposematic prey form independently of conspicuousness differences among replicas, we first modeled the visual system of a typical avian predator. Then, we used this model to estimate replica contrast against a leaf litter background to test whether variation in contrast alone could explain variation in predator attack rate. We found that absolute predation rates did not differ among color forms. Predation rates relative to conspicuousness did, however, deviate significantly from expectation, suggesting that predators do make post-detection decisions to avoid or attack a given prey type. The direction of this deviation from expectation, though, depended on assumptions we made about how avian predators discriminate objects from the visual background. Our results show that it is important to account for prey conspicuousness when investigating predator behavior and also that existing models of predator visual systems need to be refined.

  18. Nesting Bird “Host Funnel” Increases Mosquito-Bird Contact Rate

    OpenAIRE

    CAILLOUËT, KEVIN A.; RIGGAN, ANNA E.; BULLUCK, LESLEY P.; CARLSON, JOHN C.; SABO, ROY T.

    2013-01-01

    Increases in vector-host contact rates can enhance arbovirus transmission intensity. We investigated weekly fluctuations in contact rates between mosquitoes and nesting birds using the recently described Nest Mosquito Trap (NMT). The number of mosquitoes per nestling increased from < 1 mosquito per trap night to 36.2 in the final 2 wk of the nesting season. Our evidence suggests the coincidence of the end of the avian nesting season and increasing mosquito abundances may have caused a “host f...

  19. Predation as a landscape effect: the trading off by prey species between predation risks and protection benefits.

    Science.gov (United States)

    Mönkkönen, M; Husby, M; Tornberg, R; Helle, P; Thomson, R L

    2007-05-01

    1. Predators impose costs on their prey but may also provide benefits such as protection against other (e.g. nest) predators. The optimal breeding location in relation to the distance from a nesting raptor varies so as to minimize the sum of costs of adult and nest predation. We provide a conceptual model to account for variation in the relative predation risks and derive qualitative predictions for how different prey species should respond to the distance from goshawk Accipiter gentilis nests. 2. We test the model predictions using a comprehensive collection of data from northern Finland and central Norway. First, we carried out a series of experiments with artificial bird nests to test if goshawks may provide protection against nest predation. Second, we conducted standard bird censuses and nest-box experiments to detect how the density or territory occupancy of several prey species varies with distance from the nearest goshawk nest. 3. Nest predation rate increased with distance from goshawk nest indicating that goshawks may provide protection for birds' nests against nest predation. Abundance (or probability of presence) of the main prey species of goshawks peaked at intermediate distances from goshawk nests, reflecting the trade-off. The abundance of small songbird species decreased with distance from goshawk nests. The goshawk poses little risk to small songbirds and they may benefit from goshawk proximity in protection against nest predation. Finally, no pattern with distance in pied flycatcher territory (nest box) occupation rate or the onset of egg-laying was detected. This is expected, as flycatchers neither suffer from marked nest predation risk nor are favoured goshawk prey. 4. Our results suggest that territory location in relation to the nest of a predator is a trade-off situation where adult birds weigh the risk of themselves being predated against the benefits accrued from increased nest survival. Prey species appear able to detect and measure

  20. Using consumption rate to assess potential predators for biological control of white perch

    Directory of Open Access Journals (Sweden)

    Gosch N.J.C.

    2011-08-01

    Full Text Available Control of undesirable fishes is important in aquatic systems, and using predation as a tool for biological control is an attractive option to fishery biologists. However, determining the appropriate predators for biological control is critical for success. The objective of this study was to evaluate the utility of consumption rate as an index to determine the most effective predators for biological control of an invasive fish. Consumption rate values were calculated for nine potential predators that prey on white perch Morone americana in Branched Oak and Pawnee reservoirs, Nebraska. The consumption rate index provided a unique and insightful means of determining the potential effectiveness of each predator species in controlling white perch. Cumulative frequency distributions facilitated interpretation by providing a graphical presentation of consumption rates by all individuals within each predator species. Largemouth bass Micropterus salmoides, walleye Sander vitreus and sauger S. canadensis were the most efficient white perch predators in both reservoirs; however, previous attempts to increase biomass of these predators have failed suggesting that successful biological control is unlikely using existing predator species in these Nebraska reservoirs.

  1. A quantification of predation rates, indirect positive effects on plants, and foraging variation of the giant tropical ant, Paraponera clavata

    Directory of Open Access Journals (Sweden)

    Lee A. Dyer

    2002-09-01

    Full Text Available While a clear consensus is emerging that predators can play a major role in shaping terrestrial communities, basic natural history observations and simple quantifications of predation rates in complex terrestrial systems are lacking. The potential indirect effect of a large predatory ant, Paraponera clavata Fabricius (Formicidae: Ponerinae, on herbivores was determined on rainforest trees at La Selva Biological Station in Costa Rica and Barro Colorado Island in Panama. Prey and other food brought back to nests by 75 colonies of P. clavata were quantified, taking into account temporal, seasonal, and microhabitat variation for both foraging activity and composition of foraging booty. The dispersion and density of ant colonies and combined density with the mean amounts of prey retrieval were used to calculate rates of predation per hectare in the two forests. In addition, herbivory was measured on trees containing P. clavata and on trees where the ants were not foraging. Colonies at La Selva brought back significantly more nectar plus prey than those at Barro Colorado Island, but foraging patterns were similar in the two forests. At both forests, the ants were more active at night, and there was no significant seasonal or colonial variation in consumption of nectar, composition of foraging booty, and overall activity of the colonies. At La Selva, trees containing P. clavata colonies had the same levels of folivory as nearest neighbor trees without P. clavata but had significantly lower folivory than randomly selected trees. Predation by this ant was high in both forests, despite its omnivorous diet. This insect predator is part of potentially important top-down controls in these wet and moist forests.

  2. The effect of wind on the rate of heat loss from avian cup-shaped nests.

    Science.gov (United States)

    Heenan, Caragh B; Seymour, Roger S

    2012-01-01

    Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis) and yellow-throated miner (Manorina flavigula), were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success.

  3. The effect of wind on the rate of heat loss from avian cup-shaped nests.

    Directory of Open Access Journals (Sweden)

    Caragh B Heenan

    Full Text Available Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis and yellow-throated miner (Manorina flavigula, were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success.

  4. Seasonal Effects of Habitat on Sources and Rates of Snowshoe Hare Predation in Alaskan Boreal Forests.

    Directory of Open Access Journals (Sweden)

    Dashiell Feierabend

    Full Text Available Survival and predation of snowshoe hares (Lepus americanus has been widely studied, yet there has been little quantification of the changes in vulnerability of hares to specific predators that may result from seasonal changes in vegetation and cover. We investigated survival and causes of mortalities of snowshoe hares during the late increase, peak, and decline of a population in interior Alaska. From June 2008 to May 2012, we radio-tagged 288 adult and older juvenile hares in early successional and black spruce (Picea mariana forests and, using known-fate methods in program MARK, evaluated 85 survival models that included variables for sex, age, and body condition of hares, as well as trapping site, month, season, year, snowfall, snow depth, and air temperature. We compared the models using Akaike's information criterion with correction for small sample size. Model results indicated that month, capture site, and body condition were the most important variables in explaining survival rates. Survival was highest in July, and more generally during summer, when alternative prey was available to predators of hares. Low survival rates coincided with molting periods, breeding activity in the spring, and the introduction of juveniles to the sample population in the fall. We identified predation as the cause of mortality in 86% of hare deaths. When the source of predation could be determined, hares were killed more often by goshawks (Accipiter gentilis than other predators in early successional forest (30%, and more often by lynx (Lynx canadensis than other predators in black spruce forest (31%. Great horned owls (Bubo virginianus and coyotes (Canis latrans represented smaller proportions of hare predation, and non-predatory causes were a minor source (3% of mortality. Because hares rely on vegetative cover for concealment from predators, we measured cover in predation sites and habitats that the hares occupied and concluded that habitat type had a

  5. Temperature-mediated changes in rates of predator forgetting in woodfrog tadpoles.

    Directory of Open Access Journals (Sweden)

    Maud C O Ferrari

    Full Text Available Hundreds of studies have investigated the sources and nature of information that prey gather about their predators and the ways in which prey use this information to mediate their risk of predation. However, relatively little theoretical or empirical work has considered the question of how long information should be maintained and used by prey animals in making behavioural decisions. Here, we tested whether the size of the memory window associated with predator recognition could be affected by an intrinsic factor, such as size and growth rate of the prey. We maintained groups of predator-naive woodfrog, Lithobates sylvaticus, tadpoles at different temperatures for 8 days to induce differences in tadpole size. We then conditioned small and large tadpoles to recognize the odour of a predatory tiger salamander, Ambystoma tigrinum. Tadpoles were then maintained either on a high or low growth trajectory for another 8 days, after which they were tested for their response to the predator. Our results suggest that the memory window related to predator recognition of tadpoles is determined by both their size and/or growth rate at the time of learning and their subsequent growth rate post-learning.

  6. Nesting success and within-season breeding dispersal in the ...

    African Journals Online (AJOL)

    Nest predation is a primary cause of nesting mortality for many bird species, particularly passerines. Nest location can affect predation, and it has also been demonstrated that predation risk can alter nest site selection. Birds can limit predation risk by selecting specific habitat characteristics; by changing nest site ...

  7. Competition between apex predators? Brown bears decrease wolf kill rate on two continents.

    Science.gov (United States)

    Tallian, Aimee; Ordiz, Andrés; Metz, Matthew C; Milleret, Cyril; Wikenros, Camilla; Smith, Douglas W; Stahler, Daniel R; Kindberg, Jonas; MacNulty, Daniel R; Wabakken, Petter; Swenson, Jon E; Sand, Håkan

    2017-02-08

    Trophic interactions are a fundamental topic in ecology, but we know little about how competition between apex predators affects predation, the mechanism driving top-down forcing in ecosystems. We used long-term datasets from Scandinavia (Europe) and Yellowstone National Park (North America) to evaluate how grey wolf ( Canis lupus ) kill rate was affected by a sympatric apex predator, the brown bear ( Ursus arctos ). We used kill interval (i.e. the number of days between consecutive ungulate kills) as a proxy of kill rate. Although brown bears can monopolize wolf kills, we found no support in either study system for the common assumption that they cause wolves to kill more often. On the contrary, our results showed the opposite effect. In Scandinavia, wolf packs sympatric with brown bears killed less often than allopatric packs during both spring (after bear den emergence) and summer. Similarly, the presence of bears at wolf-killed ungulates was associated with wolves killing less often during summer in Yellowstone. The consistency in results between the two systems suggests that brown bear presence actually reduces wolf kill rate. Our results suggest that the influence of predation on lower trophic levels may depend on the composition of predator communities. © 2017 The Authors.

  8. Translocation of threatened New Zealand falcons to vineyards increases nest attendance, brooding and feeding rates.

    Directory of Open Access Journals (Sweden)

    Sara M Kross

    Full Text Available Anthropogenic landscapes can be rich in resources, and may in some cases provide potential habitat for species whose natural habitat has declined. We used remote videography to assess whether reintroducing individuals of the threatened New Zealand falcon Falco novaeseelandiae into a highly modified agricultural habitat affected the feeding rates of breeding falcons or related breeding behavior such as nest attendance and brooding rates. Over 2,800 recording hours of footage were used to compare the behavior of falcons living in six natural nests (in unmanaged, hilly terrain between 4 km and 20 km from the nearest vineyard, with that of four breeding falcon pairs that had been transported into vineyards and nested within 500 m of the nearest vineyard. Falcons in vineyard nests had higher feeding rates, higher nest attendance, and higher brooding rates. As chick age increased, parents in vineyard nests fed chicks a greater amount of total prey and larger prey items on average than did parents in hill nests. Parents with larger broods brought in larger prey items and a greater total sum of prey biomass. Nevertheless, chicks in nests containing siblings received less daily biomass per individual than single chicks. Some of these results can be attributed to the supplementary feeding of falcons in vineyards. However, even after removing supplementary food from our analysis, falcons in vineyards still fed larger prey items to chicks than did parents in hill nests, suggesting that the anthropogenic habitat may be a viable source of quality food. Although agricultural regions globally are rarely associated with raptor conservation, these results suggest that translocating New Zealand falcons into vineyards has potential for the conservation of this species.

  9. Do ducks and songbirds initiate more nests when the probability of survival is greater?

    Science.gov (United States)

    Grant, Todd A.; Shaffer, Terry L.

    2015-01-01

    Nesting chronology in grassland birds can vary by species, locality, and year. The date a nest is initiated can influence the subsequent probability of its survival in some grassland bird species. Because predation is the most significant cause of nest loss in grassland birds, we examined the relation between timing of nesting and nest survival. Periods of high nest survival that correspond with the peak of nesting activity might reflect long-term adaptations to specific predation pressures commonly recurring during certain periods of the nesting cycle. We evaluated this theory by comparing timing of nesting with date-specific nest survival rates for several duck and passerine species breeding in north-central North Dakota during 1998–2003. Nest survival decreased seasonally with date for five of the seven species we studied. We found little evidence to support consistent relations between timing of nesting, the number of nest initiations, and nest survival for any species we studied, suggesting that factors other than nest predation may better explain nesting chronology for these species. The apparent mismatch between date-specific patterns of nest survival and nest initiation underscores uncertainty about the process of avian nest site selection driven mainly by predation. Although timing of nesting differed among species, the general nesting period was fairly predictable across all years of study, suggesting the potential for research activities or management actions to be timed to take advantage of known periods when nests are active (or inactive). However, our results do not support the notion that biologists can take advantage of periods when many nests are active and survival is also high.

  10. Management of modern agricultural landscapes increases nest predation rates in black-tailed godwits Limosa limosa

    NARCIS (Netherlands)

    Kentie, Rosemarie; Both, Christiaan; Hooijmeijer, Jos C.E.W.; Piersma, Theunis

    Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb-rich meadows has been replaced by grassland monocultures. The timing

  11. Management of modern agricultural landscapes increases nest predation rates in Black-tailed Godwits

    NARCIS (Netherlands)

    Kentie, R.; Both, C.; Hooijmeijer, C.E.W.; Piersma, T.

    2015-01-01

    Effective conservation of endangered species requires a solid understanding of the demographic causes of population change. Bird populations breeding on agricultural grasslands have declined because their preferred habitat of herb-rich meadows has been replaced by grassland monocultures. The timing

  12. Predator attack rate evolution in space: the role of ecology mediated by complex emergent spatial structure and self-shading.

    Science.gov (United States)

    Messinger, Susanna M; Ostling, Annette

    2013-11-01

    Predation interactions are an important element of ecological communities. Population spatial structure has been shown to influence predator evolution, resulting in the evolution of a reduced predator attack rate; however, the evolutionary role of traits governing predator and prey ecology is unknown. The evolutionary effect of spatial structure on a predator's attack rate has primarily been explored assuming a fixed metapopulation spatial structure, and understood in terms of group selection. But endogenously generated, emergent spatial structure is common in nature. Furthermore, the evolutionary influence of ecological traits may be mediated through the spatial self-structuring process. Drawing from theory on pathogens, the evolutionary effect of emergent spatial structure can be understood in terms of self-shading, where a voracious predator limits its long-term invasion potential by reducing local prey availability. Here we formalize the effects of self-shading for predators using spatial moment equations. Then, through simulations, we show that in a spatial context self-shading leads to relationships between predator-prey ecology and the predator's attack rate that are not expected in a non-spatial context. Some relationships are analogous to relationships already shown for host-pathogen interactions, but others represent new trait dimensions. Finally, since understanding the effects of ecology using existing self-shading theory requires simplifications of the emergent spatial structure that do not apply well here, we also develop metrics describing the complex spatial structure of the predator and prey populations to help us explain the evolutionary effect of predator and prey ecology in the context of self-shading. The identification of these metrics may provide a step towards expansion of the predictive domain of self-shading theory to more complex spatial dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. Predação de ninhos artificiais em uma ilha na Mata Atlântica: testando o local e o tipo de ovo Artificial nest predation in Atlantic Forest Island: testing the place and the different types of egg

    Directory of Open Access Journals (Sweden)

    Ariane D. Alvarez

    2007-12-01

    Full Text Available Experimentos com ninhos artificiais são utilizados para testar hipóteses ecológicas e comportamentais que influenciam na predação de ninhos naturais. O tamanho do ovo, a textura da casca e a cor podem influenciar na taxa de predação, porém poucos estudos avaliam qual modelo de ovo é o mais adequado para simular a predação de ninhos em áreas tropicais. O objetivo deste trabalho foi comparar a predação de diferentes modelos de ovos (ovos de codorna, massa de modelar e canários no solo e a 1,30 m de altura no sub-bosque. O experimento foi realizado Ilha Anchieta, Ubatuba, São Paulo, Brasil. Foi encontrada uma diferença significativa na taxa de predação entre os ovos de codorna (71,87% e sintéticos (93,75% e entre os ovos de codorna e de canário (100% no solo. Entretanto, não houve diferença significativa entre os ovos sintéticos e de canário. Os ninhos no sub-bosque apresentaram um padrão diferenciado do solo quando se refere aos ovos de codorna (25% e sintéticos (28,1%, mas houve diferenças significativas quando os ovos de canário foram comparados com os ovos sintéticos e de codorna. Nosso trabalho demonstrou que diferentes tipos de ovos sobre uma mesma pressão de mesopredadores apresentaram taxas de predação diferentes. Portanto, estudos que avaliam o sucesso reprodutivo da avifauna baseado na predação de ninhos artificiais devem considerar a utilização de diferentes tipos de ovos e estratos na vegetação.Experiments on artificial nests are usually used to test ecological hypothesis and behavioural that affects the predation of natural bird nests. It is has been discussed about the size of the egg, texture and color affecting predation rate, but a few studies evaluate which egg type is more appropriate to simulate nest predation in tropical areas. The objective of this work was to compare the predation of different models of eggs (Coturnix coturnix, plasticine and Serinus canarius on the ground and understory

  14. The impact of rural-urban gradient and spatial distribution on predation rates on sentinel prey in a riparian forest in Hungary

    DEFF Research Database (Denmark)

    Eötvös, Csaba Béla; Magura, Tibor; Lövei, Gabor L.

    2015-01-01

    is the predation pressure in this kind of habitat? (2) What are the differences in predation between rural, suburban and urban habitats? (3) What inter-prey distances are necessary for different predator groups that the dummy caterpillars would be independent? We found 17.76% overall predation rate, decreasing...... from rural to urban habitats (33.5%, 18.29% and 3.91%, respectively). Most of the ground level arthropod predation was related to carabids. We applied variogram analysis to acquire optimal placement distances. According to our results, in case all of the predators (except mammals), 5-10 m distances......Measuring predation rates under field conditions is rife with ecological and logistical difficulties. The use of artificial sentinel prey offers a simple and cheap possibility to comparable predation activity in various habitats by various predator groups. This method can replace the classical...

  15. The influence of nest-site characteristics on the nesting success of ...

    African Journals Online (AJOL)

    Choice of nest site has important consequences for nest survival. We examined nest-site characteristics relative to nest success in Karoo Prinias breeding in coastal dwarf shrubland, where high nest predation is the main cause of nest failure. Initially, we compared nests that failed during the building, laying, incubation and ...

  16. Nested radiations and the pulse of angiosperm diversification: increased diversification rates often follow whole genome duplications.

    Science.gov (United States)

    Tank, David C; Eastman, Jonathan M; Pennell, Matthew W; Soltis, Pamela S; Soltis, Douglas E; Hinchliff, Cody E; Brown, Joseph W; Sessa, Emily B; Harmon, Luke J

    2015-07-01

    Our growing understanding of the plant tree of life provides a novel opportunity to uncover the major drivers of angiosperm diversity. Using a time-calibrated phylogeny, we characterized hot and cold spots of lineage diversification across the angiosperm tree of life by modeling evolutionary diversification using stepwise AIC (MEDUSA). We also tested the whole-genome duplication (WGD) radiation lag-time model, which postulates that increases in diversification tend to lag behind established WGD events. Diversification rates have been incredibly heterogeneous throughout the evolutionary history of angiosperms and reveal a pattern of 'nested radiations' - increases in net diversification nested within other radiations. This pattern in turn generates a negative relationship between clade age and diversity across both families and orders. We suggest that stochastically changing diversification rates across the phylogeny explain these patterns. Finally, we demonstrate significant statistical support for the WGD radiation lag-time model. Across angiosperms, nested shifts in diversification led to an overall increasing rate of net diversification and declining relative extinction rates through time. These diversification shifts are only rarely perfectly associated with WGD events, but commonly follow them after a lag period. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  17. An assessment of the efficacy and peak catch rates of emergence tents for measuring bee nesting.

    Science.gov (United States)

    Pane, Alexander M; Harmon-Threatt, Alexandra N

    2017-06-01

    Emergence tents are a new tool used to understand nesting ecology of ground nesting bee species. However, many questions remain about how to use tents effectively. We assessed (a) variance in tent capture rates over time, (b) the effects of site characteristics on proportion of tents capturing bees, and (c) the effect of soil characteristics on nest site choice. Emergence tents were placed out for one week in May, June, and August and checked daily. Soil, bee, and floral characteristics were recorded. Across all sites and months the average number of tents capturing bees was less than 20% during one week of sampling, but this varied between sites. Tent captures decreased after 48 h deployment, but accumulation differed seasonally, with slower accumulation of total bees caught in May than in June or August. Although capture rates were not affected by bee or floral abundance, soil moisture beneath a tent influenced where bees were captured. Effective use of emergence tents may require adjusting the length of deployment depending on season and will require a minimum of 48 h installation to help maximize efficacy. The overall low capture rates demonstrate the need to optimize emergence tent use.

  18. Influence of container design on predation rate of potential biocontrol agent, Toxorhynchites splendens (Diptera: Culicidae) against dengue vector.

    Science.gov (United States)

    Mohamad, N; Zuharah, W F

    2014-03-01

    Toxorhynchites splendens larvae are a natural predator of dengue vector mosquito larvae, Aedes albopictus. This study was carried out to evaluate the predation rate of Tx. splendens third instar larvae on Ae. albopictus larvae in 24 h. Each predator was offered prey at a density between 10 to 50 individuals. Predation rate of Tx. splendens were also tested with two manipulated factors; various types of container and different water volumes. The experiment was evaluated in man-made containers (tin cans, plastic drinking glasses and rubber tires) and natural container (bamboo stumps) which were filled with different water volumes (full, half full, 1/4 full, and 1/8 full). The prey density and the characteristics of the container were found as significant factors which influence the predation rate of Tx. splendens. The predator consumed significantly more prey at higher prey densities (40 and 50 preys) compared to the lowest density (10 preys) (F=3.935, df=4, p=0.008). The results showed significantly higher consumption in horizontal shaped container of rubber tire than in vertical shape of bamboo stumps (F=3.100, df=3, p=0.029). However, the water volume had no significant effect on predation rate of Tx. splendens (F=1.736, df=3, p=0.162). We generally suggest that Tx. splendens is best to be released in discarded tires or any other containers with horizontal shape design with wide opening since Tx. splendens can become more effective in searching prey in this type of container design. This predator is also a suitable biocontrol candidates to be introduced either in wet and dry seasons in Malaysia.

  19. Circumpolar dynamics of a marine top-predator track ocean warming rates.

    Science.gov (United States)

    Descamps, Sébastien; Anker-Nilssen, Tycho; Barrett, Robert T; Irons, David B; Merkel, Flemming; Robertson, Gregory J; Yoccoz, Nigel G; Mallory, Mark L; Montevecchi, William A; Boertmann, David; Artukhin, Yuri; Christensen-Dalsgaard, Signe; Erikstad, Kjell-Einar; Gilchrist, H Grant; Labansen, Aili L; Lorentsen, Svein-Håkon; Mosbech, Anders; Olsen, Bergur; Petersen, Aevar; Rail, Jean-Francois; Renner, Heather M; Strøm, Hallvard; Systad, Geir H; Wilhelm, Sabina I; Zelenskaya, Larisa

    2017-09-01

    Global warming is a nonlinear process, and temperature may increase in a stepwise manner. Periods of abrupt warming can trigger persistent changes in the state of ecosystems, also called regime shifts. The responses of organisms to abrupt warming and associated regime shifts can be unlike responses to periods of slow or moderate change. Understanding of nonlinearity in the biological responses to climate warming is needed to assess the consequences of ongoing climate change. Here, we demonstrate that the population dynamics of a long-lived, wide-ranging marine predator are associated with changes in the rate of ocean warming. Data from 556 colonies of black-legged kittiwakes Rissa tridactyla distributed throughout its breeding range revealed that an abrupt warming of sea-surface temperature in the 1990s coincided with steep kittiwake population decline. Periods of moderate warming in sea temperatures did not seem to affect kittiwake dynamics. The rapid warming observed in the 1990s may have driven large-scale, circumpolar marine ecosystem shifts that strongly affected kittiwakes through bottom-up effects. Our study sheds light on the nonlinear response of a circumpolar seabird to large-scale changes in oceanographic conditions and indicates that marine top predators may be more sensitive to the rate of ocean warming rather than to warming itself. © 2017 John Wiley & Sons Ltd.

  20. Feeding rates, double brooding, nest reuse, and seasonal fecundity of eastern wood-pewees in the Missouri Ozarks

    Science.gov (United States)

    Sarah W. Kendrick; Frank R. III Thompson; Jennifer L. Reidy

    2014-01-01

    Despite being widespread and abundant, little is known about the breeding ecology and natural history of the Eastern Wood-Pewee (Contopus virens), in part because nests are often high in the canopy, difficult to view, and adults are monomorphic. We monitored nests of Eastern Wood-Pewees and recorded the feeding rate of nestlings by adults as part of...

  1. Daily nest survival rates of Gunnison Sage-Grouse (Centrocercus minimus): assessing local- and landscape-scale drivers

    Science.gov (United States)

    Stanley, Thomas R.; Aldridge, Cameron L.; Joanne Saher,; Theresa Childers,

    2015-01-01

    The Gunnison Sage-Grouse (Centrocercus minimus) is a species of conservation concern and is a candidate for listing under the U.S. Endangered Species Act because of substantial declines in populations from historic levels. It is thought that loss, fragmentation, and deterioration of sagebrush (Artemisia spp.) habitat have contributed to the decline and isolation of this species into seven geographically distinct subpopulations. Nest survival is known to be a primary driver of demography of Greater Sage-Grouse (C. urophasianus), but no unbiased estimates of daily nest survival rates (hereafter nest survival) exist for Gunnison Sage-Grouse or published studies identifying factors that influence nest survival. We estimated nest survival of Gunnison Sage-Grouse for the western portion of Colorado's Gunnison Basin subpopulation, and assessed the effects and relative importance of local- and landscape-scale habitat characteristics on nest survival. Our top performing model was one that allowed variation in nest survival among areas, suggesting a larger landscape-area effect. Overall nest success during a 38-day nesting period (egg-laying plus incubation) was 50% (daily survival rate; SE  =  0.982 [0.003]), which is higher than previous estimates for Gunnison Sage-Grouse and generally higher than published for the closely related Greater Sage-Grouse. We did not find strong evidence that local-scale habitat variables were better predictors of nest survival than landscape-scale predictors, nor did we find strong evidence that any of the habitat variables we measured were good predictors of nest survival. Nest success of Gunnison Sage-Grouse in the western portion of the Gunnison Basin was higher than previously believed.

  2. Differential effects of coyotes and red foxes on duck nest success

    Science.gov (United States)

    Sovada, Marsha A.; Sargeant, A.; Grier, J.W.

    1995-01-01

    Low recruitment rates prevail among ducks in the Prairie Pothole Region of North America, primarily because of high nest depredation rates. The red fox (Vulpes vulpes) is a major predator of duck eggs, but fox abundance is depressed by coyotes (Canis latrans). We tested the hypothesis that nest success of upland-nesting ducks is higher in areas with coyotes than in areas with red foxes. We conducted the study during 1990-92 in uplands of 36 areas managed for nesting ducks in North Dakota and South Dakota. Overall nest success averaged 32% (95% CI = 25-40) on 17 study areas where coyotes were the principal canid and 17% (CI = 11-25) on 13 study areas where red foxes were the principal canid (P = 0.01). Both canids were common on 6 other areas, where nest success averaged 25% (CI = 13-47). Habitat composition, predator communities with the exception of canids, and species composition of duck nests in coyote and red fox areas were similar overall. Upon examining only nests with greater than or equal to 6 eggs on the last visit prior to hatch or depredation, we determined nests with evidence characteristic of fox predation accounted for 4% of depredated nests in coyote areas and 27% in fox areas (P = 0.001). An expanding coyote population is contributing to higher overall nest success. Management of coyotes may be an effective method for increasing duck nest success.

  3. Plasticity of parental care under the risk of predation: how much should parents reduce care?

    Science.gov (United States)

    Martin, Thomas E.

    2013-01-01

    Predation can be an important agent of natural selection shaping parental care behaviours, and can also favour behavioural plasticity. Parent birds often decrease the rate that they visit the nest to provision offspring when perceived risk is high. Yet, the plasticity of such responses may differ among species as a function of either their relative risk of predation, or the mean rate of provisioning. Here, we report parental provisioning responses to experimental increases in the perceived risk of predation. We tested responses of 10 species of bird in north temperate Arizona and subtropical Argentina that differed in their ambient risk of predation. All species decreased provisioning rates in response to the nest predator but not to a control. However, provisioning rates decreased more in species that had greater ambient risk of predation on natural nests. These results support theoretical predictions that the extent of plasticity of a trait that is sensitive to nest predation risk should vary among species in accordance with predation risk.

  4. Hard times in the city - attractive nest sites but insufficient food supply lead to low reproduction rates in a bird of prey.

    Science.gov (United States)

    Sumasgutner, Petra; Nemeth, Erwin; Tebb, Graham; Krenn, Harald W; Gamauf, Anita

    2014-01-01

    Urbanization is a global phenomenon that is encroaching on natural habitats and decreasing biodiversity, although it is creating new habitats for some species. The Eurasian kestrel (Falco tinnunculus) is frequently associated with urbanized landscapes but it is unclear what lies behind the high densities of kestrels in the urban environment. Occupied nest sites in the city of Vienna, Austria were investigated along a gradient of urbanization (percentage of land covered by buildings or used by traffic). Field surveys determined the abundance of potential prey (birds and rodents) and the results were compared to the birds' diets. A number of breeding parameters were recorded over the course of three years. The majority of kestrels breed in semi-natural cavities in historic buildings. Nearest neighbour distances (NND) were smallest and reproductive success lowest in the city centre. Abundance of potential prey was not found to relate to the degree of urbanization but there was a significant shift in the birds' diets from a heavy reliance on rodents in the outskirts of the city to feeding more on small birds in the centre. The use of urban habitats was associated with higher nest failure, partly associated with predation and nest desertion, and with significantly lower hatching rates and smaller fledged broods. High breeding densities in urban habitats do not necessarily correlate with high habitat quality. The high density of kestrel nests in the city centre is probably due to the ready availability of breeding cavities. Highly urbanized areas in Vienna are associated with unexpected costs for the city dwelling-raptor, in terms both of prey availability and of reproductive success. The kestrel appears to be exploiting the urban environment but given the poor reproductive performance of urban kestrels it is likely that the species is falling into an ecological trap.

  5. Hard times in the city – attractive nest sites but insufficient food supply lead to low reproduction rates in a bird of prey

    Science.gov (United States)

    2014-01-01

    Introduction Urbanization is a global phenomenon that is encroaching on natural habitats and decreasing biodiversity, although it is creating new habitats for some species. The Eurasian kestrel (Falco tinnunculus) is frequently associated with urbanized landscapes but it is unclear what lies behind the high densities of kestrels in the urban environment. Results Occupied nest sites in the city of Vienna, Austria were investigated along a gradient of urbanization (percentage of land covered by buildings or used by traffic). Field surveys determined the abundance of potential prey (birds and rodents) and the results were compared to the birds’ diets. A number of breeding parameters were recorded over the course of three years. The majority of kestrels breed in semi-natural cavities in historic buildings. Nearest neighbour distances (NND) were smallest and reproductive success lowest in the city centre. Abundance of potential prey was not found to relate to the degree of urbanization but there was a significant shift in the birds’ diets from a heavy reliance on rodents in the outskirts of the city to feeding more on small birds in the centre. The use of urban habitats was associated with higher nest failure, partly associated with predation and nest desertion, and with significantly lower hatching rates and smaller fledged broods. Conclusions High breeding densities in urban habitats do not necessarily correlate with high habitat quality. The high density of kestrel nests in the city centre is probably due to the ready availability of breeding cavities. Highly urbanized areas in Vienna are associated with unexpected costs for the city dwelling-raptor, in terms both of prey availability and of reproductive success. The kestrel appears to be exploiting the urban environment but given the poor reproductive performance of urban kestrels it is likely that the species is falling into an ecological trap. PMID:24872836

  6. Linking Life Table and Predation Rate for Biological Control: A Comparative Study of Eocanthecona furcellata (Hemiptera: Pentatomidae) Fed on Spodoptera litura (Lepidoptera: Noctuidae) and Plutella xylostella (Lepidoptera: Plutellidae).

    Science.gov (United States)

    Tuan, Shu-Jen; Yeh, Chih-Chun; Atlihan, Remzi; Chi, Hsin

    2016-02-01

    To better understand the predator-prey relationship and to compare predation rates, we studied the life table and predation rate of the predator Eocanthecona furcellata Wolff (Hemiptera: Pentatomidae) when reared on two major crucifer pests, Spodoptera litura (F.) (Lepidoptera: Noctuidae) and Plutella xylostella L. (Lepidoptera: Plutellidae). The net reproductive rate, intrinsic rate of increase, finite rate, and net predation rates of E. furcellata reared on P. xylostella were 292.4 offspring, 0.1389 d(-1), 1.1490 d(-1), and 644.1 third instars of P. xylostella, respectively. These values are significantly higher than those reared on S. litura, i.e., 272.3 offspring, 0.1220 d(-1), 1.1298 d(-1), and 863.1 third instars of S. litura. To evaluate the predation potential of E. furcellata fed on P. xylostella and S. litura, we combined both the growth rate and predation rate to calculate the finite predation rate (ω); our results showed that E. furcellata is an effective predator of both S. litura (ω = 1.6029) and P. xylostella (ω = 1.4277). © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Intraguild predation reduces redundancy of predator species in multiple predator assemblage.

    Science.gov (United States)

    Griffen, Blaine D; Byers, James E

    2006-07-01

    1. Interference between predator species frequently decreases predation rates, lowering the risk of predation for shared prey. However, such interference can also occur between conspecific predators. 2. Therefore, to understand the importance of predator biodiversity and the degree that predator species can be considered functionally interchangeable, we determined the degree of additivity and redundancy of predators in multiple- and single-species combinations. 3. We show that interference between two invasive species of predatory crabs, Carcinus maenas and Hemigrapsus sanguineus, reduced the risk of predation for shared amphipod prey, and had redundant per capita effects in most multiple- and single-species predator combinations. 4. However, when predator combinations with the potential for intraguild predation were examined, predator interference increased and predator redundancy decreased. 5. Our study indicates that trophic structure is important in determining how the effects of predator species combine and demonstrates the utility of determining the redundancy, as well as the additivity, of multiple predator species.

  8. Observer visitation frequency and success of mourning dove nests: A field experiment

    Science.gov (United States)

    Nichols, J.D.; Percival, H.F.; Coon, R.A.; Conroy, M.J.; Hensler, G.L.; Hines, J.E.

    1984-01-01

    Field studies of nesting success generally require visits by the investigator to the nests under study. Such visits may themselves influence nesting success, however, and this possibility has been discussed and investigated by a number of workers with a variety of bird species. Livezey (1980) reviewed the relevant literature for duck nests and noted that most studies failed to demonstrate differences in nesting success between visited nests and those not visited. Livezey (1980) found in his own work that nest abandonment may have occurred as a result of disturbance by observers but that nest predation was not related to time spent by observers at nests or number of observers approaching nests. Various components of nesting and breeding success in seabirds are thought to be adversely affected by human disturbance and nest visitation (Gillett et al. 1975, Robert and Ralph 1975, Ollason and Dunnet 1980). Upland, ground-nesting species have also been studied (e.g. Stoddard 1931, Evans and Wolfe 1967, Henry 1969, Roseberry and Klimstra 1970, Klimstra and Roseberry 1975), and, although conclusions have varied, a number of these workers found no effect of observers on nest-predation rates.

  9. Clearance rates of jellyfish and their potential predation impact on zooplankton and fish larvae in a neritic ecosystem (Limfjorden, Denmark)

    DEFF Research Database (Denmark)

    Hansson, L. J.; Moeslund, O.; Kiørboe, Thomas

    2005-01-01

    clearance potential were given assumed clearance rate values, but the collective predation potential by these species was evaluated to be small. Hydromedusae dominated numerically and had their highest potential clearance impact in spring, but overall jellyfish clearance potential on copepods was low during...

  10. Experimental evidence for innate predator recognition in the Seychelles warbler

    NARCIS (Netherlands)

    Veen, Thor; Richardson, David S.; Blaakmeer, Karen; Komdeur, Jan

    2000-01-01

    Nest predation is a major determinant of fitness in birds and costly nest defence behaviours have evolved in order to reduce nest predation. Some avian studies have suggested that predator recognition is innate whereas others hate stressed the importance: of learning. However, none of these studies

  11. Encounter rates and swimming behavior of pause-travel and cruise larval fish predators in calm and turbulent laboratory environments

    DEFF Research Database (Denmark)

    MacKenzie, Brian; Kiørboe, Thomas

    1995-01-01

    measure of prey encounter rate in unsatiated larvae) were significantly higher in turbulent than in calm water at low food abundances for two size groups of cod. The difference in cod attack position rate between calm and turbulent water was much less when prey was more abundant. Attack position rates...... of herring larvae were higher in turbulent water than in calm water, but the difference was not significant. Interspecific differences in swimming and pausing behavior were related to differences in prey search strategy used by the two species (cod: pause-travel; herring: cruise). We used a newly developed...... search model for pause-travel predators in calm and turbulent environments to compare encounter rates for predators using cruise and pause-travel search strategies. Encounter rates for cod and herring larvae, estimated with respective search models, were similar in calm and low turbulence water; at high...

  12. Immune-related effects from predation risk in Neotropical blue-black grassquits (Volatinia jacarina).

    Science.gov (United States)

    Caetano, João V O; Maia, Maya R; Manica, Lilian T; Macedo, Regina H

    2014-11-01

    Predation is a major force shaping natural history traits of birds because of their vulnerability during nesting and higher visibility during diurnal activities. For most birds in the Neotropics, predation is the major cause of nest failure due to the region's high diversity and abundance of predators. The blue-black grassquit (Volatinia jacarina), similarly to other small passerines in the savanna region of central Brazil, suffers extremely high rates of nest predation. Additionally, males may be particularly vulnerable to predators since they are very conspicuous when executing courtship displays. We assessed some of the non-lethal costs of predation risk on this species by comparing physiological and morphological parameters of birds exposed to predator vocalizations with that of control subjects exposed to non-predator vocalizations. Birds exposed to the predator vocalizations exhibited an immune-related reaction (changes in their H/L ratio), but no changes were observed in other biological parameters measured. This article is part of a Special Issue entitled: Neotropical Behaviour. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Feeding Activity, Rate of Consumption, Daily Ration and Prey Selection of Major Predators in John Day Reservoir, 1985: Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, Douglas E.; United States. Bonneville Power Administration; U.S. Fish and Wildlife Service; National Fishery Research Center (U.S.)

    1986-10-01

    This report summarizes activities in 1985 to determine the extent of predation on juvenile salmonids in John Day Reservoir. To estimate consumption of juvenile salmonids we used the composition of the natural diet of predators and in the laboratory determined rate of gastric evacuation by predators. Salmonids were the single most important food item for northern squawfish (Ptychocheilus oregonensis) at McNary tailrace during all sampling periods and at John Day forebay during July. Salmonids accounted for 11.6% of the diet of walleye (Stizostedion vitreum vitreum) in 1985 which was about twice that found in previous years. Salmonids contributed little to smallmouth bass (Micropterus dolomieui) diet but comprised about 25% of the diet of channel catfish (Ictalurus punctatus). Composition of prey taxa in beach seine catches in 1985 was similar to 1983 and 1984 with chinook salmon (Oncorhynchus tschawytscha), northern squawfish, largescale sucker (Catostomus macrocheilus), and sand roller (Percopsis transmontana) dominating the catch at main channel stations and crappies (Pomoxis spp.) and largescale sucker dominating at backwater stations. Preliminary results of beach seine efficiency studies suggest that seine efficiency varied significantly among prey species and between substrate types in 1985. Results of digestion rate experiments indicate that gastric evacuation in northern squawfish can be predicted using water temperature, prey weight, predator weight and time. 19 refs., 19 figs., 13 tabs.

  14. A method for in situ estimation of prey selectivity and predation rate in large plankton, exemplified with the jellyfish Aurelia aurita (L.)

    DEFF Research Database (Denmark)

    Hansson, L.J.

    2006-01-01

    , predation rate can be calculated as increase in gut content over time. Clearance rates for different prey can be calculated from predation rates and prey concentrations in the water, allowing accurate estimates of prey selectivity. Thus, the problem of unknown feeding history and feeding environment, which...... of a specific individual plankton predator in situ.After prey has been evacuated from the gut of an individual predator, the predator is incubated in situ, and observed by SCUBA-divers who recapture the individual after a defined time. Given that this incubation time is shorter than prey digestion time...... among individual jellyfish and among the various oral arms and gastric pouches within individuals. Clearance rates varied strongly with prey type. The medusae selected large crustacean prey (cladocerans and copepods/copepodites) over echinoderm larvae and copepod nauplii. Prey distribution within...

  15. Habitat selection responses of parents to offspring predation risk: An experimental test

    Science.gov (United States)

    Fontaine, J.J.; Martin, T.E.

    2006-01-01

    The ability of nest predation to influence habitat settlement decisions in birds is widely debated, despite its importance in limiting fitness. Here, we experimentally manipulated nest predation risk across a landscape and asked the question, do migratory birds assess and respond to variation in nest predation risk when choosing breeding habitats? We examined habitat preference by quantifying the density and settlement date of eight species of migratory passerines breeding in areas with and without intact nest predator communities. We found consistently more individuals nesting in areas with reduced nest predation than in areas with intact predator assemblages, although predation risk had no influence on settlement or breeding phenology. Additionally, those individuals occupying safer nesting habitats exhibited increased singing activity. These findings support a causal relationship between habitat choice and nest predation risk and suggest the importance of nest predation risk in shaping avian community structure and breeding activity. ?? 2006 by The University of Chicago. All rights reserved.

  16. Effect of food on immature development, consumption rate, and relative growth rate of Toxorhynchites splendens (Diptera: Culicidae, a predator of container breeding mosquitoes

    Directory of Open Access Journals (Sweden)

    D Dominic Amalraj

    2005-12-01

    Full Text Available Food utilization by the larvae of Toxorhynchites splendens (Wiedemann was studied in the laboratory by offering larvae of Aedes aegypti Linnaeus, Anopheles stephensi (Liston, and Culex quinquefasciatus (Say. Quantitative analyses of data indicated that immature development was significantly faster with increase in food availability. The regression analysis showed that the degrees of the relationship between immature duration (Id and food availability were higher when offered early instars of prey (first and second instars than late instars. Consumption rate (Cr of the predator increased with increase in food availability and this relationship was highly significant when larvae of An. stephensi were offered as food. Consumption rate to food level decreased with increase in the age class of the prey. There was a significant negative correlation between Id and Cr. This aspect helps to increase population turnover of T. splendens in a shorter period when the prey is abundant. Conversely, the predator compensated the loss in daily food intake at low food level by extending Id thereby attains the minimum threshold pupal weight for adult emergence. There was an increase in the relative growth rate (RGR of the predator when An. stephensi was offered as prey and this was related to the high protein content of the prey per body weight. There was a positive correlation between Cr and RGR. This adaptive life characteristic strategy of this predator is useful for mass-rearing for large scale field release programmes in the control of container breeding mosquitoes is discussed.

  17. Nest Construction by a Ground-nesting Bird Represents a Potential Trade-off Between Egg Crypticity and Thermoregulation

    Science.gov (United States)

    Predation selects against conspicuous colors in bird eggs and nests, while thermoregulatory constraints select for nest building behavior that regulates incubation temperatures. We present results that reveal a trade-off between nest crypticity and thermoregulation of eggs base...

  18. Predator guild does not influence orangutan alarm call rates and combinations

    NARCIS (Netherlands)

    Lameira, A.R.; de Vries, H.; Hardus, M.E.; Hall, C.P.A.; Mitra-Setia, T.; Spruijt, B.M.; Kershenbaum, A.; Sterck, E.H.M.; van Noordwijk, M.; van Schaick, C.; Wich, S.A.

    2013-01-01

    Monkey alarm calls have shown that in the primate clade, combinatorial rules in acoustic communication are not exclusive to humans. A recent hypothesis suggests that the number of different call combinations in monkeys increases with increased number of predator species. However, the existence of

  19. Nest mortality of sagebrush songbirds due to a severe hailstorm

    Science.gov (United States)

    Hightower, Jessica N.; Carlisle, Jason D.; Chalfoun, Anna D.

    2018-01-01

    Demographic assessments of nesting birds typically focus on failures due to nest predation or brood parasitism. Extreme weather events such as hailstorms, however, can also destroy eggs and injure or kill juvenile and adult birds at the nest. We documented the effects of a severe hailstorm on 3 species of sagebrush-associated songbirds: Sage Thrasher (Oreoscoptes montanus), Brewer's Sparrow (Spizella breweri), and Vesper Sparrow (Pooecetes gramineus), nesting at eight 24 ha study plots in central Wyoming, USA. Across all plots, 17% of 128 nests failed due to the hailstorm; however, all failed nests were located at a subset of study plots (n = 3) where the hailstorm was most intense, and 45% of all nests failures on those plots were due to hail. Mortality rates varied by species, nest architecture, and nest placement. Nests with more robust architecture and those sited more deeply under the shrub canopy were more likely to survive the hailstorm, suggesting that natural history traits may modulate mortality risk due to hailstorms. While sporadic in nature, hailstorms may represent a significant source of nest failure to songbirds in certain locations, especially with increasing storm frequency and severity forecasted in some regions with ongoing climate change.

  20. The Great Basin Canada goose in southcentral Washington: A 40-year nesting history

    International Nuclear Information System (INIS)

    Fitzner, R.E.; Rickard, W.H.; Eberhardt, L.E.; Gray, R.H.

    1991-04-01

    Overall, the nesting population of Great Basin Canada geese (Branta canadensis moffitti) on the Hanford Site in southcentral Washington State is doing well and appears to be increasing. The average annual total nests for the period 1981 through 1990 was 215 nests, which is slightly above the average reported for the period 1950 through 1970. The nesting population has shifted its nucleus from upriver islands (1--10) to the lower river islands (11--20) with over 70% of the present-day nesting occurring on Islands 17, 18, 19, 20. The annual percent-successful nests from 1981 through 1990 was 80%. This is above the 71% reported for 1950 to 1970, but is below the 82% reported for 1971 to 1980. Average annual clutch size for 1981 to 1990 was 6.05, which is above the 1971-to-1980 average of 5.6 and the 1950-to-70 average of 5.5. Next desertions for 1981 to 1990 averaged 8%. This rate is well below the 14% reported for 1950 to 1970. Predators were responsible for an annual predation rate of 9% from 1981 to 1990. This is below the 1950-to-1970 annual average predation rate of 14%. Flooding losses to nests were low during the 1980s, except for 1989 and 1990 when 6% and 9% of the total nests, respectively, were destroyed by flooding. 9 refs., 4 figs., 1 tab

  1. Influence of olfactory and visual cover on nest site selection and nest success for grassland-nesting birds.

    Science.gov (United States)

    Fogarty, Dillon T; Elmore, R Dwayne; Fuhlendorf, Samuel D; Loss, Scott R

    2017-08-01

    Habitat selection by animals is influenced by and mitigates the effects of predation and environmental extremes. For birds, nest site selection is crucial to offspring production because nests are exposed to extreme weather and predation pressure. Predators that forage using olfaction often dominate nest predator communities; therefore, factors that influence olfactory detection (e.g., airflow and weather variables, including turbulence and moisture) should influence nest site selection and survival. However, few studies have assessed the importance of olfactory cover for habitat selection and survival. We assessed whether ground-nesting birds select nest sites based on visual and/or olfactory cover. Additionally, we assessed the importance of visual cover and airflow and weather variables associated with olfactory cover in influencing nest survival. In managed grasslands in Oklahoma, USA, we monitored nests of Northern Bobwhite ( Colinus virginianus ), Eastern Meadowlark ( Sturnella magna ), and Grasshopper Sparrow ( Ammodramus savannarum ) during 2015 and 2016. To assess nest site selection, we compared cover variables between nests and random points. To assess factors influencing nest survival, we used visual cover and olfactory-related measurements (i.e., airflow and weather variables) to model daily nest survival. For nest site selection, nest sites had greater overhead visual cover than random points, but no other significant differences were found. Weather variables hypothesized to influence olfactory detection, specifically precipitation and relative humidity, were the best predictors of and were positively related to daily nest survival. Selection for overhead cover likely contributed to mitigation of thermal extremes and possibly reduced detectability of nests. For daily nest survival, we hypothesize that major nest predators focused on prey other than the monitored species' nests during high moisture conditions, thus increasing nest survival on these

  2. Nest-site selection and success of mottled ducks on agricultural lands in southwest Louisiana

    Science.gov (United States)

    Durham, R.S.; Afton, A.D.

    2003-01-01

    Listing of the mottled duck (Anas fulvigula maculosa) as a priority species in the Gulf Coast Joint Venture of the North American Waterfowl Management Plan, coupled with recent declines of rice (Oryza sativa) acreage, led us to investigate the nesting ecology of this species on agricultural lands in southwest Louisiana. We examined nest-site selection at macro- and microhabitat levels, nest success, causes of nest failures, and habitat features influencing nest success. We found that female mottled ducks preferred to nest in permanent pastures with knolls (53% of nests) and idle fields (22% of nests). Vegetation height was greater at nests than at random points within the same macrohabitat patch. Successful nests were associated with greater numbers of plant species, located farther from water, and associated with higher vegetation density values than were unsuccessful nests. We determined that mammalian predators caused most nest failures (77% of 52 unsuccessful nests). Our results suggest that nest success of mottled ducks on agricultural lands in southwest Louisiana could be improved by 1) locating large permanent pastures and idle fields near rice fields and other available wetlands, 2) managing plant communities in these upland areas to favor dense stands of perennial bunch grasses, tall composites, dewberry (Rubus trivialis), and other native grasses and forbs, and 3) managing cattle-stocking rates and the duration and timing of grazing to promote tall, dense stands of these plant taxa during the nesting season (March-June).

  3. Impact of nest predators, competitors, and ectoparasites on Pearly-eyed Thrashers, with comments on the potential implications for Puerto Rican Parrot recovery

    Science.gov (United States)

    Wayne J. Arendt

    2000-01-01

    Over the past 17 years, research on a rain forest population of the Pearly-eyed Thrasher (Margarops fuscatus), with additional observations on nesting Puerto Rican Parrots (Amazona vittata) within the Sierra de Luquillo, Puerto Rico, has shown that reproductive success of thrashers and parrots is often greatly reduced as a result of the additive effects of a diverse...

  4. Great spotted cuckoo nestlings have no antipredatory effect on magpie or carrion crow host nests in southern Spain.

    Science.gov (United States)

    Soler, Manuel; de Neve, Liesbeth; Roldán, María; Pérez-Contreras, Tomás; Soler, Juan José

    2017-01-01

    Host defences against cuckoo parasitism and cuckoo trickeries to overcome them are a classic example of antagonistic coevolution. Recently it has been reported that this relationship may turn to be mutualistic in the case of the carrion crow (Corvus corone) and its brood parasite, the great spotted cuckoo (Clamator glandarius), given that experimentally and naturally parasitized nests were depredated at a lower rate than non-parasitized nests. This result was interpreted as a consequence of the antipredatory properties of a fetid cloacal secretion produced by cuckoo nestlings, which presumably deters predators from parasitized host nests. This potential defensive mechanism would therefore explain the detected higher fledgling success of parasitized nests during breeding seasons with high predation risk. Here, in a different study population, we explored the expected benefits in terms of reduced nest predation in naturally and experimentally parasitized nests of two different host species, carrion crows and magpies (Pica pica). During the incubation phase non-parasitized nests were depredated more frequently than parasitized nests. However, during the nestling phase, parasitized nests were not depredated at a lower rate than non-parasitized nests, neither in magpie nor in carrion crow nests, and experimental translocation of great spotted cuckoo hatchlings did not reveal causal effects between parasitism state and predation rate of host nests. Therefore, our results do not fit expectations and, thus, do not support the fascinating possibility that great spotted cuckoo nestlings could have an antipredatory effect for host nestlings, at least in our study area. We also discuss different possibilities that may conciliate these with previous results, but also several alternative explanations, including the lack of generalizability of the previously documented mutualistic association.

  5. Reduction in predator defense in the presence of neighbors in a colonial fish.

    Directory of Open Access Journals (Sweden)

    Franziska C Schädelin

    Full Text Available Predation pressure has long been considered a leading explanation of colonies, where close neighbors may reduce predation via dilution, alarming or group predator attacks. Attacking predators may be costly in terms of energy and survival, leading to the question of how neighbors contribute to predator deterrence in relationship to each other. Two hypotheses explaining the relative efforts made by neighbors are byproduct-mutualism, which occurs when breeders inadvertently attack predators by defending their nests, and reciprocity, which occurs when breeders deliberately exchange predator defense efforts with neighbors. Most studies investigating group nest defense have been performed with birds. However, colonial fish may constitute a more practical model system for an experimental approach because of the greater ability of researchers to manipulate their environment. We investigated in the colonial fish, Neolamprologus caudopunctatus, whether prospecting pairs preferred to breed near conspecifics or solitarily, and how breeders invested in anti-predator defense in relation to neighbors. In a simple choice test, prospecting pairs selected breeding sites close to neighbors versus a solitary site. Predators were then sequentially presented to the newly established test pairs, the previously established stimulus pairs or in between the two pairs. Test pairs attacked the predator eight times more frequently when they were presented on their non-neighbor side compared to between the two breeding sites, where stimulus pairs maintained high attack rates. Thus, by joining an established pair, test pairs were able to reduce their anti-predator efforts near neighbors, at no apparent cost to the stimulus pairs. These findings are unlikely to be explained by reciprocity or byproduct-mutualism. Our results instead suggest a commensal relationship in which new pairs exploit the high anti-predator efforts of established pairs, which invest similarly with or

  6. Evidence for an edge effect on avian nest predation in fragmented afromontane forests in the Bamenda-Banso Highlands, NW Cameroon

    Czech Academy of Sciences Publication Activity Database

    Sedláček, O.; Mikeš, M.; Albrecht, Tomáš; Reif, J.; Hořák, D.

    2014-01-01

    Roč. 7, č. 4 (2014), s. 720-732 ISSN 1940-0829 R&D Projects: GA ČR(CZ) GAP505/11/1617 Institutional support: RVO:68081766 Keywords : Artificial nest s * Zebra finch eggs * Montane forest * Endemic species * Cameroon Mountains Subject RIV: EG - Zoology Impact factor: 1.125, year: 2014 http://tropicalconservationscience.mongabay.com/content/v7/TCS-2014-Vol7(4)_720-732_%20Ondrej.pdf

  7. Colonial waterbird predation on Lost River and shortnose suckers based on recoveries of passive integrated transponder tags

    Science.gov (United States)

    Evans, Allen; Payton, Quinn; Cramer, Bradley D.; Collis, Ken; Hewitt, David A.; Roby, Daniel D.

    2015-01-01

    We evaluated predation on Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris), both listed under the Endangered Species Act (ESA), from American white pelicans (Pelecanus erythrorhynchos) and double-crested cormorants (Phalacrocorax auritus) nesting at mixed species colonies on Clear Lake Reservoir, CA and Upper Klamath Lake, OR during 2009-2014. Predation was evaluated by recovering passive integrated transponder (PIT) tags that were implanted in suckers, subsequently consumed by pelicans or cormorants, and deposited on the birds’ nesting colonies. Data from PIT tag recoveries were used to estimate predation rates (proportion of available tagged suckers consumed) by birds to evaluate the relative susceptibility of suckers to avian predation in Upper Klamath Basin. Data on the size of pelican and cormorant colonies (number of breeding adults) at Clear Lake and Upper Klamath Lake were also collected and reported in the context of predation on suckers.

  8. Phenology largely explains taller grass at successful nests in greater sage-grouse.

    Science.gov (United States)

    Smith, Joseph T; Tack, Jason D; Doherty, Kevin E; Allred, Brady W; Maestas, Jeremy D; Berkeley, Lorelle I; Dettenmaier, Seth J; Messmer, Terry A; Naugle, David E

    2018-01-01

    Much interest lies in the identification of manageable habitat variables that affect key vital rates for species of concern. For ground-nesting birds, vegetation surrounding the nest may play an important role in mediating nest success by providing concealment from predators. Height of grasses surrounding the nest is thought to be a driver of nest survival in greater sage-grouse ( Centrocercus urophasianus ; sage-grouse), a species that has experienced widespread population declines throughout their range. However, a growing body of the literature has found that widely used field methods can produce misleading inference on the relationship between grass height and nest success. Specifically, it has been demonstrated that measuring concealment following nest fate (failure or hatch) introduces a temporal bias whereby successful nests are measured later in the season, on average, than failed nests. This sampling bias can produce inference suggesting a positive effect of grass height on nest survival, though the relationship arises due to the confounding effect of plant phenology, not an effect on predation risk. To test the generality of this finding for sage-grouse, we reanalyzed existing datasets comprising >800 sage-grouse nests from three independent studies across the range where there was a positive relationship found between grass height and nest survival, including two using methods now known to be biased. Correcting for phenology produced equivocal relationships between grass height and sage-grouse nest survival. Viewed in total, evidence for a ubiquitous biological effect of grass height on sage-grouse nest success across time and space is lacking. In light of these findings, a reevaluation of land management guidelines emphasizing specific grass height targets to promote nest success may be merited.

  9. Theoretical study and control optimization of an integrated pest management predator-prey model with power growth rate.

    Science.gov (United States)

    Sun, Kaibiao; Zhang, Tonghua; Tian, Yuan

    2016-09-01

    This work presents a pest control predator-prey model, where rate of change in prey density follows a scaling law with exponent less than one and the control is by an integrated management strategy. The aim is to investigate the change in system dynamics and determine a pest control level with minimum control price. First, the dynamics of the proposed model without control is investigated by taking the exponent as an index parameter. And then, to determine the frequency of spraying chemical pesticide and yield releases of the predator, the existence of the order-1 periodic orbit of the control system is discussed in cases. Furthermore, to ensure a certain robustness of the adopted control, i.e., for an inaccurately detected species density or a deviation, the control system could be stabilized at the order-1 periodic orbit, the stability of the order-1 periodic orbit is verified by an stability criterion for a general semi-continuous dynamical system. In addition, to minimize the total cost input in pest control, an optimization problem is formulated and the optimum pest control level is obtained. At last, the numerical simulations with a specific model are carried out to complement the theoretical results. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Density and success of bird nests relative to grazing on western Montana grasslands

    Science.gov (United States)

    Fondell, Thomas F.; Ball, I.J.

    2004-01-01

    Grassland birds are declining at a faster rate than any other group of North American bird species. Livestock grazing is the primary economic use of grasslands in the western United States, but the effects of this use on distribution and productivity of grassland birds are unclear. We examined nest density and success of ground-nesting birds on grazed and ungrazed grasslands in western Montana. In comparison to grazed plots, ungrazed plots had reduced forb cover, increased litter cover, increased litter depth, and increased visual obstruction readings (VOR) of vegetation. Nest density among 10 of 11 common bird species was most strongly correlated with VOR of plots, and greatest nest density for each species occurred where mean VOR of the plot was similar to mean VOR at nests. Additionally, all bird species were relatively consistent in their choice of VOR at nests despite substantial differences in VOR among plots. We suggest that birds selected plots based in part on availability of suitable nest sites and that variation in nest density relative to grazing reflected the effect of grazing on availability of nest sites. Nest success was similar between grazed plots and ungrazed plots for two species but was lower for nests on grazed plots than on ungrazed plots for two other species because of increased rates of predation, trampling, or parasitism by brown-headed cowbirds (Molothrus ater). Other species nested almost exclusively on ungrazed plots (six species) or grazed plots (one species), precluding evaluation of the effects of grazing on nest success. We demonstrate that each species in a diverse suite of ground-nesting birds preferentially used certain habitats for nesting and that grazing altered availability of preferred nesting habitats through changes in vegetation structure and plant species composition. We also show that grazing directly or indirectly predisposed some bird species to increased nesting mortality. Management alternatives that avoid

  11. Hurricane disturbance benefits nesting American Oystercatchers (Haematopus palliatus)

    Science.gov (United States)

    Simons, Theodore R.; Schulte, Shiloh A.

    2016-01-01

    Coastal ecosystems are under increasing pressure from human activity, introduced species, sea level rise, and storm activity. Hurricanes are a powerful destructive force, but can also renew coastal habitats. In 2003, Hurricane Isabel altered the barrier islands of North Carolina, flattening dunes and creating sand flats. American Oystercatchers (Haematopus palliatus) are large shorebirds that inhabit the coastal zone throughout the year. Alternative survival models were evaluated for 699 American Oystercatcher nests on North Core Banks and South Core Banks, North Carolina, USA, from 1999–2007. Nest survival on North Core Banks increased from 0.170 (SE = 0.002) to 0.772 (SE = 0.090) after the hurricane, with a carry-over effect lasting 2 years. A simple year effects model described nest survival on South Core Banks. Habitat had no effect on survival except when the overall rate of nest survival was at intermediate levels (0.300–0.600), when nests on open flats survived at a higher rate (0.600; SE = 0.112) than nests in dune habitat (0.243; SE = 0.094). Predator activity declined on North Core Banks after the hurricane and corresponded with an increase in nest survival. Periodic years with elevated nest survival may offset low annual productivity and contribute to the stability of American Oystercatcher populations.

  12. Assessment of predation risk through referential communication in incubating birds

    Science.gov (United States)

    Suzuki, Toshitaka N.

    2015-05-01

    Parents of many bird species produce alarm calls when they approach and deter a nest predator in order to defend their offspring. Alarm calls have been shown to warn nestlings about predatory threats, but parents also face a similar risk of predation when incubating eggs in their nests. Here, I show that incubating female Japanese great tits, Parus minor, assess predation risk by conspecific alarm calls given outside the nest cavity. Tits produce acoustically discrete alarm calls for different nest predators: “jar” calls for snakes and “chicka” calls for other predators such as crows and martens. Playback experiments revealed that incubating females responded to “jar” calls by leaving their nest, whereas they responded to “chicka” calls by looking out of the nest entrance. Since snakes invade the nest cavity, escaping from the nest helps females avoid snake predation. In contrast, “chicka” calls are used for a variety of predator types, and therefore, looking out of the nest entrance helps females gather information about the type and location of approaching predators. These results show that incubating females derive information about predator type from different types of alarm calls, providing a novel example of functionally referential communication.

  13. Risky business for a juvenile marine predator? Testing the influence of foraging strategies on size and growth rate under natural conditions.

    Science.gov (United States)

    Hussey, Nigel E; DiBattista, Joseph D; Moore, Jonathan W; Ward, Eric J; Fisk, Aaron T; Kessel, Steven; Guttridge, Tristan L; Feldheim, Kevin A; Franks, Bryan R; Gruber, Samuel H; Weideli, Ornella C; Chapman, Demian D

    2017-04-12

    Mechanisms driving selection of body size and growth rate in wild marine vertebrates are poorly understood, thus limiting knowledge of their fitness costs at ecological, physiological and genetic scales. Here, we indirectly tested whether selection for size-related traits of juvenile sharks that inhabit a nursery hosting two dichotomous habitats, protected mangroves (low predation risk) and exposed seagrass beds (high predation risk), is influenced by their foraging behaviour. Juvenile sharks displayed a continuum of foraging strategies between mangrove and seagrass areas, with some individuals preferentially feeding in one habitat over another. Foraging habitat was correlated with growth rate, whereby slower growing, smaller individuals fed predominantly in sheltered mangroves, whereas larger, faster growing animals fed over exposed seagrass. Concomitantly, tracked juveniles undertook variable movement behaviours across both the low and high predation risk habitat. These data provide supporting evidence for the hypothesis that directional selection favouring smaller size and slower growth rate, both heritable traits in this shark population, may be driven by variability in foraging behaviour and predation risk. Such evolutionary pathways may be critical to adaptation within predator-driven marine ecosystems. © 2017 The Author(s).

  14. Age and breeding success related to nest position in a White stork Ciconia ciconia colony

    Science.gov (United States)

    Vergara, Pablo; Aguirre, José I.

    2006-11-01

    Coloniality is a breeding system that may produce benefits in terms of breeding success, although these advantages could vary according to factors such as colony size or nest position. We studied breeder's age in relation to nest position (peripheral or central) within the colony. In addition, we studied the relationship between breeding success and nest position, controlling for breeder's age, a highly correlated factor, in a White Stork Ciconia ciconia colony over a 7-year period. Our results show that central nests are mainly occupied by adult birds and had lower failure rates. However, controlling for breeder's age, nest position per se did not explain breeding success. The scarce predation and the lack of human disturbance in the study colony could explain the absence of differences in breeding success between different nest positions within the colony.

  15. Sandhill crane abundance and nesting ecology at Grays Lake, Idaho

    Science.gov (United States)

    Austin, J.E.; Henry, A.R.; Ball, I.J.

    2007-01-01

    We examined population size and factors influencing nest survival of greater sandhill cranes (Grus canadensis tabida) at Grays Lake National Wildlife Refuge, Idaho, USA, during 1997-2000. Average local population of cranes from late April to early May, 1998-2000, was 735 cranes, 34% higher than that reported for May 1970-1971. We estimated 228 (SE = 30) nests in the basin core (excluding renests), 14% higher than a 1971 estimate. Apparent nest success in our study (x?? = 60%, n = 519 nests) was lower than reported for Grays Lake 30-50 years earlier. Daily survival rates (DSRs) of all nests averaged 0.9707 (41.2%). The best model explaining nest survival included year and water depth and their interaction. Nest survival was highest (DSR = 0.9827) in 1998 compared with other years (0.9698-0.9707). Nest survival changed little relative to water depth in 1998, when flooding was extensive and alternative prey (microtines) irrupted, but declined markedly with lower water levels in 2000, the driest year studied. Hypotheses relating nest survival to vegetation height, land use (idle, summer grazing, fall grazing), and date were not supported. In a before-after-control-impact design using 12 experimental fields, nest survival differed among years but not among management treatments (idle, fall graze, fall burn, and summer-graze-idle rotation), nor was there an interaction between year and treatments. However, DSRs in fall-burn fields declined from 0.9781 in 1997-1998 to 0.9503 in 1999-2000 (posttreatment). Changes in the predator community have likely contributed to declines in nest success since the 1950s and 1970s. Our results did not support earlier concerns about effects of habitat management practices on crane productivity. Nest survival could best be enhanced by managing spring water levels. Managers should continue censuses during late April to evaluate long-term relationships to habitat conditions and management.

  16. Nesting ecology of Arctic loons

    Science.gov (United States)

    Petersen, Margaret R.

    1979-01-01

    Arctic Loons were studied on the Yukon-Kuskokwim Delta, Alaska, from the time of their arrival in May to their departure in September, in 1974 and 1975. Pairs arrived on breeding ponds as soon as sufficient meltwater was available to allow their take-off and landing. Loons apparently do not initiate nests immediately after their arrival, even when nest-sites are available. Delayed egg-laying may be dependent on a period of yolk formation. Delaying yolk formation until after arrival on nest ponds is an adaptation by loons to the variable time suitable habitat becomes available for nesting. Predation of eggs by Glaucous Gulls, Long-tailed and Parasitic jaegers and foxes varied in relation to the location of the nest-site, and the availability of alternate prey. Hatching success was the lowest recorded for Arctic Loons (5%) in 1974, when eggs of both loons and Cackling Geese were taken in large numbers by predators. Hatching success increased to 32% in 1975 when an abundance of tundra voles was observed. No loon eggs hatched after the hatching of the Cackling Goose eggs when this alternate prey was no longer available. Nests destroyed by foxes were predominantly along shorelines, and those by gulls and jaegers were predominantly on islands. Nest-site selection by Arctic Loons may reflect an adaptive response to varying selective pressures by their predators.

  17. Factors affecting nesting success in the Great-crested Grebe ...

    African Journals Online (AJOL)

    The overall nesting success was 70.4% (N = 209), with nest failure caused mainly by predation (65%) and flooding (23%). Breeding outcome was significantly and positively related to nest size, with bigger nests conferring better survival to eggs and young probably through affording better protection during spells of adverse ...

  18. The influence of anti-predator training, personality and sex in the behavior, dispersion and survival rates of translocated captive-raised parrots

    Directory of Open Access Journals (Sweden)

    Alice R.S. Lopes

    2017-07-01

    Full Text Available Predation is one of the main factors responsible for the failure of reintroduction/translocation programs. Animal's personality and sex can also influence key behaviors for survival and reproduction. This study aimed to evaluate the influence of anti-predator training, personality and sex on the survival and behaviors of translocated blue-fronted Amazon parrots. Thirty-one captive-raised parrots were translocated to a Cerrado area in Brazil. Parrots were separated into two groups: anti-predator trained group (ATG and control group (CG. Personality tests were performed with individuals of the ATG group. Data were collected using focal sampling with instantaneous recording of behavior every minute. Anti-predator training, personality and sex did not influenced parrots' survival after release. However, anti-predator training proved to be efficient in eliciting more natural behaviors in parrots after release. Shy individuals and males showed to be more sociable than bold individuals and females. Personality and sex did not influence behavior exhibition. Parrots interacted more, positively or negatively, with individuals of its own group. Training session closer to the release date should be tried. Behavioral data and not just survival rates should be used to evaluate the efficiency of the techniques, because behavior can give clues about the adaptation of the individuals to the new habitat, increasing the success of the conservation program.

  19. Breeding performance of blue tits (Cyanistes cæruleus ultramarinus) in relation to lead pollution and nest failure rates in rural, intermediate, and urban sites in Algeria.

    Science.gov (United States)

    Brahmia, Zahra; Scheifler, Renaud; Crini, Nadia; Maas, Samuel; Giraudoux, Patrick; Benyacoub, Slim

    2013-03-01

    The breeding parameters and the egg and nestling morphology of Cyanistes caeruleus populations from rural, intermediate, and urban sites in Algeria and the relationships of those variables with lead contamination were studied during three consecutive years. Breeding success was explained only by predation and vandalism rates. Predation was higher in the rural area, whereas vandalism was higher in the urban site. The other measured breeding parameters and egg characteristics were relatively insensitive to study site. The morphology of urban nestlings exhibited a trend toward smaller body size and mass compared to individuals from intermediate and rural sites. Although lead concentrations were higher in the tissues of urban birds than in intermediate and rural individuals, we did not detect a clear influence of this variable on nestling morphology. We conclude that urbanization influenced blue tit breeding parameters through predation and vandalism and nestling morphology through mechanisms other than lead pollution. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Avian nestling predation by endangered Mount Graham red squirrel

    Science.gov (United States)

    Claire A. Zugmeyer; John L. Koprowski

    2007-01-01

    Studies using artificial nests or remote cameras have documented avian predation by red squirrels (Tamiasciurus hudsonicus). Although several direct observations of avian predation events are known in the northern range of the red squirrel distribution, no accounts have been reported in the southern portion. We observed predation upon a hermit thrush...

  1. Warm water and cool nests are best. How global warming might influence hatchling green turtle swimming performance.

    Directory of Open Access Journals (Sweden)

    David T Booth

    Full Text Available For sea turtles nesting on beaches surrounded by coral reefs, the most important element of hatchling recruitment is escaping predation by fish as they swim across the fringing reef, and as a consequence hatchlings that minimize their exposure to fish predation by minimizing the time spent crossing the fringing reef have a greater chance of surviving the reef crossing. One way to decrease the time required to cross the fringing reef is to maximize swimming speed. We found that both water temperature and nest temperature influence swimming performance of hatchling green turtles, but in opposite directions. Warm water increases swimming ability, with hatchling turtles swimming in warm water having a faster stroke rate, while an increase in nest temperature decreases swimming ability with hatchlings from warm nests producing less thrust per stroke.

  2. Unusual raptor nests around the world

    Science.gov (United States)

    Ellis, D.H.; Craig, T.; Craig, E.; Postupalsky, S.; LaRue, C.T.; Nelson, R.W.; Anderson, D.W.; Henny, C.J.; Watson, J.; Millsap, B.A.; Dawson, J.W.; Cole, K.L.; Martin, E.M.; Margalida, A.; Kung, P.

    2009-01-01

    From surveys in many countries, we report raptors using unusual nesting materials (e.g., paper money, rags, metal, antlers, and large bones) and unusual nesting situations. For example, we documented nests of Steppe Eagles Aquila nipalensis and Upland Buzzards Buteo hemilasius on the ground beside well-traveled roads, Saker Falcon Falco cherrug eyries in attics and a cistern, and Osprey Pandion haliaetus nests on the masts of boats and on a suspended automobile. Other records include a Golden Eagle A. chrysaetos nest 7.0 m in height, believed to be the tallest nest ever described, and, for the same species, we report nesting in rudimentary nests. Some nest sites are within a few meters of known predators or competitors. These unusual observations may be important in revealing the plasticity of a species' behavioral repertoire. ?? 2009 The Raptor Research Foundation, Inc.

  3. Birds' nesting parameters in four forest types in the Pantanal wetland

    Directory of Open Access Journals (Sweden)

    JB Pinho

    Full Text Available We tested the heterogeneity/productivity hypothesis with respect to the abundance and richness of birds and the vegetation density hypothesis with respect to birds' nest predation rates, and determined the relative importance of forested vegetation formations for the conservation of birds in the Pantanal. We estimated the apparent nesting success, and the abundance and richness of nesting birds' in four forest types, by monitoring nests during two reproductive seasons in four forested physiognomies (two high productivity/heterogeneity evergreen forests = Cambará and Landi; two low productivity/heterogeneity dry forests = Cordilheira and Carvoeiro in the Pantanal wetland in Poconé, State of Mato Grosso, Brazil. We found 381 nests of 46 species (35 Passeriformes and 11 non-Passeriformes in the four forest types. Of these, we monitored 220 active nests belonging to 44 species, 101 during the reproductive season of 2001 and 119 in 2002. We supported the productivity/heterogeneity hypothesis since the two evergreen forests had higher nest abundance and one of them (Cambará had higher nesting species richness than the dry forests. The number of nests found in each habitat differed with most nests monitored in the Cambará forest (82%, followed by Landi (9%, Cordilheira (6% and Carvoeiro (3% forests. The total number of nests monitored was significantly higher in evergreen forests than in dry forests. Also, more species nested in evergreen (37 species than in dry (16 species forests. A Correspondence Analysis revealed that only Carvoeiros had a different nesting bird community. The overall apparent nesting success of 220 nests was 26.8%. We did not support the vegetation density hypothesis since nest predation rates were similar between evergreen (73.5% and dry (70% forests, and were higher in the Landi (85% than in the other three forests (69.2 to 72.2%. Our data indicate that Cambará forests seem to be a key nesting habitat for many bird species

  4. Birds' nesting parameters in four forest types in the Pantanal wetland.

    Science.gov (United States)

    Pinho, J B; Marini, M A

    2014-11-01

    We tested the heterogeneity/productivity hypothesis with respect to the abundance and richness of birds and the vegetation density hypothesis with respect to birds' nest predation rates, and determined the relative importance of forested vegetation formations for the conservation of birds in the Pantanal. We estimated the apparent nesting success, and the abundance and richness of nesting birds' in four forest types, by monitoring nests during two reproductive seasons in four forested physiognomies (two high productivity/heterogeneity evergreen forests = Cambará and Landi; two low productivity/heterogeneity dry forests = Cordilheira and Carvoeiro) in the Pantanal wetland in Poconé, State of Mato Grosso, Brazil. We found 381 nests of 46 species (35 Passeriformes and 11 non-Passeriformes) in the four forest types. Of these, we monitored 220 active nests belonging to 44 species, 101 during the reproductive season of 2001 and 119 in 2002. We supported the productivity/heterogeneity hypothesis since the two evergreen forests had higher nest abundance and one of them (Cambará) had higher nesting species richness than the dry forests. The number of nests found in each habitat differed with most nests monitored in the Cambará forest (82%), followed by Landi (9%), Cordilheira (6%) and Carvoeiro (3%) forests. The total number of nests monitored was significantly higher in evergreen forests than in dry forests. Also, more species nested in evergreen (37 species) than in dry (16 species) forests. A Correspondence Analysis revealed that only Carvoeiros had a different nesting bird community. The overall apparent nesting success of 220 nests was 26.8%. We did not support the vegetation density hypothesis since nest predation rates were similar between evergreen (73.5%) and dry (70%) forests, and were higher in the Landi (85%) than in the other three forests (69.2 to 72.2%). Our data indicate that Cambará forests seem to be a key nesting habitat for many bird species of the

  5. Red fox predation on breeding ducks in midcontinent North America

    Science.gov (United States)

    Sargeant, Alan B.; Allen, Stephen H.; Eberhardt, Robert T.

    1984-01-01

    Red fox (Vulpes vulpes) predation on nesting ducks was assessed by examining 1,857 adult duck remains found at 1,432 fox rearing dens from 1968 to 1973. Dabbling ducks were much more vulnerable to foxes than diving ducks. Dabbling ducks (1,798) found at dens consisted of 27% blue-winged teals (Anas discors), 23% mallards (A. platyrhynchos), 20% northern pintails (A. acuta), 9% northern shovelers (Spatula clypeata), 8% gadwalls (A. strepera), 3% green-winged teals (A. crecca), 2% American wigeons (A. americana), and 10% unidentified. Relative abundance of individual species and nesting chronology were the most important factors affecting composition of ducks taken by foxes. Seventy-six percent of 1,376 adult dabbling ducks and 40% of 30 adult diving ducks for which sex was determined were hens. In western North Dakota and western South Dakota, 65% of mallard and northern pintail remains found at dens were hens compared with 76% in eastern North Dakota and eastern South Dakota (P fox predation rates on ducks. Predation rate indices ranged from 0.01 duck/den in Iowa to 1.80 ducks/den in eastern North Dakota. Average annual predation rate indices for dabbling ducks in a 3-county intensive study area in eastern North Dakota were closely correlated with May pond numbers (r = 0.874, P foxes than hens of late nesting species. Predation rate indices were expanded to estimate total numbers of ducks taken by fox families during the denning season. Estimated numbers of dabbling ducks taken annually by individual fox families in 2 physiographic regions comprising the intensive study area ranged from 16.1 to 65.9. Predation was highest during wet years and lowest during dry years and averaged lower, but was more variable, in the region where tillage was greatest and wetland water levels were least stable. Predation in the intensive study area averaged 2.97 adult dabbling ducks/ km2/year and represented an estimated average annual loss of 13.5% of hen and 4.5% of drake

  6. Bird species diversity and nesting success in mature, clearcut and shelterwood forest in northern New Hampshire, USA

    Science.gov (United States)

    David I. King; Richard M. DeGraaf

    2000-01-01

    Bird species distribution and predation rates on natural and artificial nests were compared among unmanaged mature, shelterwood, and clearcut northern hardwoods forest to evaluate the effect of these practices on bird populations. Twenty-three of the 48 bird species detected during the study differed significantly in abundance among unmanaged mature forest,...

  7. Tagging Piglets at the Farrowing Nest in the Wild: Some Preliminary Guidelines

    Directory of Open Access Journals (Sweden)

    BAUBET, Eric

    2009-01-01

    Full Text Available Neonate ungulate often show high rates of mortality due to predation, starvation, orexposure to bad weather, leading to losses frequently exceeding 50%. Wild boar piglets are known tosuffer from thermoregulation insufficiency, which probably explain the nest construction behaviour insows. We thus tried to develop a method for tagging piglets inside their farrowing (or birth nest toassess piglet survival from few days after their birth onwards. Sows fitted-out with VHF collars wereradio-tracked to determine parturition time, and to get a rough idea of the possible birth nest location.Then, with a handled antenna we approached on foot the birth nest, and piglets were caught, taggedand fitted-out with a backpack transmitter and released inside the nest. Temporal movements ofmother and litter association were monitored, as long as possible. Results on sow behaviour and tacticagainst human approach, piglets body mass, piglet reaction, and survival in their early lifetime weredescribed.

  8. Nest site selection of the Southern Pale Chanting Goshawk in the ...

    African Journals Online (AJOL)

    This study investigated whether Southern Pale Chanting Goshawks Melierax canorus that est in the low woody vegetation of the arid Little Karoo reduce nest predation by selecting nest trees and sites that are less accessible to and conspicuous for terrestrial predators. The 114 nest trees and shrubs sampled were taller (0 ...

  9. Colonial waterbird predation on Lost River and Shortnose suckers in the Upper Klamath Basin

    Science.gov (United States)

    Evans, Allen F.; Hewitt, David A.; Payton, Quinn; Cramer, Bradley M.; Collis, Ken; Roby, Daniel D.

    2016-01-01

    We evaluated predation on Lost River Suckers Deltistes luxatus and Shortnose Suckers Chasmistes brevirostris by American white pelicans Pelecanus erythrorhynchos and double-crested cormorants Phalacrocorax auritus nesting at mixed-species colonies in the Upper Klamath Basin of Oregon and California during 2009–2014. Predation was evaluated by recovering (detecting) PIT tags from tagged fish on bird colonies and calculating minimum predation rates, as the percentage of available suckers consumed, adjusted for PIT tag detection probabilities but not deposition probabilities (i.e., probability an egested tag was deposited on- or off-colony). Results indicate that impacts of avian predation varied by sucker species, age-class (adult, juvenile), bird colony location, and year, demonstrating dynamic predator–prey interactions. Tagged suckers ranging in size from 72 to 730 mm were susceptible to cormorant or pelican predation; all but the largest Lost River Suckers were susceptible to bird predation. Minimum predation rate estimates ranged annually from <0.1% to 4.6% of the available PIT-tagged Lost River Suckers and from <0.1% to 4.2% of the available Shortnose Suckers, and predation rates were consistently higher on suckers in Clear Lake Reservoir, California, than on suckers in Upper Klamath Lake, Oregon. There was evidence that bird predation on juvenile suckers (species unknown) in Upper Klamath Lake was higher than on adult suckers in Upper Klamath Lake, where minimum predation rates ranged annually from 5.7% to 8.4% of available juveniles. Results suggest that avian predation is a factor limiting the recovery of populations of Lost River and Shortnose suckers, particularly juvenile suckers in Upper Klamath Lake and adult suckers in Clear Lake Reservoir. Additional research is needed to measure predator-specific PIT tag deposition probabilities (which, based on other published studies, could increase predation rates presented herein by a factor of roughly 2

  10. Feeding Activity, Rate of Consumption, Daily Ration and Prey Selection of Major Predators in John Day Reservoir, 1984 : Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Gerard A.; United States. Bonneville Power Administration; U.S. Fish and Wildlife Service; National Fishery Research Center (U.S.)

    1986-07-01

    The extent of predation on juvenile salmonids in John Day Reservoir was determined. Salmonids were the single most important food item by weight for northern squawfish (Ptychocheilus oregonensis) in the restricted zones at McNary tailrace and John Day forebay during all sampling periods. Salmonids accounted for 18.1% of the weight in the diet of walleyes (Stizostedion vitreum vitreum) in 1984 which was at least twice that found in previous years. In smallmouth bass (Micropterus dolomieui) salmonids contributed little to their diet whereas for channel catfish (Ictalurus punctatus) fish accounted for 64.1% of the weight in their diet with salmonids responsible for approximately half of this weight. An intensive search of the fisheries literature was conducted to review various fish capture and control techniques which might have potential as predation control measures for the major predators of juvenile salmonids in the Columbia River system. Most prey protection measures were judged to have high potential and direct predator control measures were judged to have moderate or low potential.

  11. Variation in clutch size in relation to nest size in birds

    OpenAIRE

    Moller Anders P.; Adriaensen Frank; Artemyev Alexandr; Banbura Jerzy; Barba Emilio; Biard Clotilde; Blondel Jacques; Bouslama Zihad; Bouvier Jean-Charles; Camprodon Jordi; Cecere Francesco; Charmantier Anne; Charter Motti; Cichon Mariusz; Cusimano Camillo

    2014-01-01

    © 2014 The Authors. Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited...

  12. Nest-site partitioning in a strandveld shrubland bird community ...

    African Journals Online (AJOL)

    Nest-site selection may vary adaptively among co-existing species as a result of competitive interactions among the species or in response to density-dependent nest predation. We examined nest-site characteristics and degree of partitioning among 14 co-existing bird species breeding in dwarf strandveld shrubland at ...

  13. Triangular Nests!

    Science.gov (United States)

    Powell, R. I.

    2002-01-01

    Shows how integer-sided triangles can be nested, each nest having a single enclosing isosceles triangle. Brings to light what can be seen as a relatively simple generalization of Pythagoras' theorem, a result that should be readily accessible to many secondary school pupils. (Author/KHR)

  14. Bald eagle predation on common loon egg

    Science.gov (United States)

    DeStefano, Stephen; McCarthy, Kyle P.; Laskowski, Tom

    2010-01-01

    The Common Loon (Gavia immer) must defend against many potential egg predators during incubation, including corvids, Herring Gulls (Larus argentatus), raccoons (Procyon lotor), striped skunk (Mephitis mephitis), fisher (Martes pennanti), and mink (Neovison vison) (McIntyre 1988, Evers 2004, McCann et al. 2005). Bald Eagles (Haliaeetus leucocephalus) have been documented as predators of both adult Common Loons and their chicks (Vliestra and Paruk 1997, Paruk et al. 1999, Erlandson et al. 2007, Piper et al. 2008). In Wisconsin, where nesting Bald Eagles are abundant (>1200 nesting pairs, >1 young/pair/year), field biologists observed four instances of eagle predation of eggs in loon nests during the period 2002–2004 (M. Meyer pers. comm.). In addition, four cases of eagle predation of incubating adult loons were inferred from evidence found at the loon nest (dozens of plucked adult loon feathers, no carcass remains) and/or loon leg, neck, and skull bones beneath two active eagle nests, including leg bones containing the bands of the nearby (nest surveillance video camera on Lake Umbagog, a large lake (32 km2) at Umbagog National Wildlife Refuge (UNWR) in Maine.

  15. Breeding performance of blue tits (Cyanistes cæruleus ultramarinus) in relation to lead pollution and nest failure rates in rural, intermediate, and urban sites in Algeria

    International Nuclear Information System (INIS)

    Brahmia, Zahra; Scheifler, Renaud; Crini, Nadia; Maas, Samuel; Giraudoux, Patrick; Benyacoub, Slim

    2013-01-01

    The breeding parameters and the egg and nestling morphology of Cyanistes caeruleus populations from rural, intermediate, and urban sites in Algeria and the relationships of those variables with lead contamination were studied during three consecutive years. Breeding success was explained only by predation and vandalism rates. Predation was higher in the rural area, whereas vandalism was higher in the urban site. The other measured breeding parameters and egg characteristics were relatively insensitive to study site. The morphology of urban nestlings exhibited a trend toward smaller body size and mass compared to individuals from intermediate and rural sites. Although lead concentrations were higher in the tissues of urban birds than in intermediate and rural individuals, we did not detect a clear influence of this variable on nestling morphology. We conclude that urbanization influenced blue tit breeding parameters through predation and vandalism and nestling morphology through mechanisms other than lead pollution. -- Highlights: ► Life history traits in relation to lead contamination were studied in blue tits from rural, industrial and urban sites. ► The study took place in Annaba, the fourth most populated city of Algeria, during 3 consecutive years. ► Breeding success depended on predation and vandalism, which were high in the rural and urban sites, respectively. ► Urban nestlings exhibited a trend toward smaller body size and mass, which was not explained by lead contamination. ► Urbanization influences breeding success and nestling morphology in blue tits through other mechanisms than lead pollution. -- Urbanization modifies the nestling morphology and breeding success of populations of the Algerian blue tit (Cyanistes caeruleus ultramarinus) through mechanisms other than lead pollution

  16. Relationship between survival rate of avian artificial nests and forest vegetation structure along a tropical altitudinal gradient on Mount Cameroon

    Czech Academy of Sciences Publication Activity Database

    Djomo Nana, E.; Sedláček, O.; Doležal, Jiří; Dančák, Martin; Altman, Jan; Svoboda, M.; Majeský, L.; Hořák, D.

    2015-01-01

    Roč. 47, č. 6 (2015), s. 758-764 ISSN 0006-3606 R&D Projects: GA ČR(CZ) GAP505/11/1617 Institutional support: RVO:67985939 Keywords : artificial nest s * vegetation parameters * West-Central Africa Subject RIV: EH - Ecology, Behaviour Impact factor: 1.944, year: 2015

  17. Enhanced detection rate of typhoid fever among clinically suspected patients in a tertiary referral hospital in Dhaka, Bangladesh using nested polymerase chain reaction technology.

    Science.gov (United States)

    Khan, S; Miah, M R; Khatun, S

    2015-12-01

    A nested polymerase chain reaction (PCR) specific for Salmonella enterica subspecies enteric serovar Typhi was used for the detection of the pathogen, in blood. This study was done during the period of March 2013 to February 2014. A total of 80 clinically suspected cases of typhoid fever were included in the study. Blood was collected from all participating individuals. Nested PCR targeting the flagellin gene (fliC) of Salmonella Typhi & blood culture were done for each of the cases. The positivity rate of PCR & blood culture was 70%& 20% respectively. The positivity rate of PCR was significantly higher than blood culture (Ptyphoid fever cases on the basis of clinical features but with negative cultures. We conclude that the PCR technique could be used as a novel diagnostic method of typhoid fever, particularly in culture-negative cases in an endemic country like Bangladesh.

  18. Importance of structural stability to success of mourning dove nests

    Science.gov (United States)

    Coon, R.A.; Nichols, J.D.; Percival, H.F.

    1981-01-01

    Studies of nest-site selection and nesting habitats often involve a "characterization" of nests and of habitats in which nests are found. Our objective in the present work is to identify nest-site characteristics that are associated with variation in components of Mourning Dove (Zenaida macroura) fitness (e.g. the probability of a nest succeeding), as opposed to simply "characterizing" dove nest sites. If certain nest- site characteristics affect the probability that a nest will succeed, then we suspect that these characteristics will be associated with either concealment (the probability of detection by certain predators) or structural stability (the probability of eggs or entire nests falling to the ground as a result of wind, rain storms, parental activity, etc.). Although other workers agree that structural stability is an important determinant of Mourning Dove nesting success (e.g. McClure 1944: 384; Woolfenden and Rohwer 1969: 59), we are aware of no actual tests of this hypothesis.

  19. Introduced mammalian predators induce behavioural changes in parental care in an endemic New Zealand bird.

    Directory of Open Access Journals (Sweden)

    Melanie Massaro

    Full Text Available The introduction of predatory mammals to oceanic islands has led to the extinction of many endemic birds. Although introduced predators should favour changes that reduce predation risk in surviving bird species, the ability of island birds to respond to such novel changes remains unstudied. We tested whether novel predation risk imposed by introduced mammalian predators has altered the parental behaviour of the endemic New Zealand bellbird (Anthornis melanura. We examined parental behaviour of bellbirds at three woodland sites in New Zealand that differed in predation risk: 1 a mainland site with exotic predators present (high predation risk, 2 a mainland site with exotic predators experimentally removed (low risk recently and, 3 an off-shore island where exotic predators were never introduced (low risk always. We also compared parental behaviour of bellbirds with two closely related Tasmanian honeyeaters (Phylidonyris spp. that evolved with native nest predators (high risk always. Increased nest predation risk has been postulated to favour reduced parental activity, and we tested whether island bellbirds responded to variation in predation risk. We found that females spent more time on the nest per incubating bout with increased risk of predation, a strategy that minimised activity at the nest during incubation. Parental activity during the nestling period, measured as number of feeding visits/hr, also decreased with increasing nest predation risk across sites, and was lowest among the honeyeaters in Tasmania that evolved with native predators. These results demonstrate that some island birds are able to respond to increased risk of predation by novel predators in ways that appear adaptive. We suggest that conservation efforts may be more effective if they take advantage of the ability of island birds to respond to novel predators, especially when the elimination of exotic predators is not possible.

  20. Introduced mammalian predators induce behavioural changes in parental care in an endemic New Zealand bird

    Science.gov (United States)

    Massaro, M.; Starling-Windhof, A.; Briskie, J.V.; Martin, T.E.

    2008-01-01

    The introduction of predatory mammals to oceanic islands has led to the extension of many birds. Although introduced predators should favour changes that reduce predation risk in surviving bird species, the ability of island birds to respond to such novel changes remains unstudied. We tested whether novel predation risk imposed by introduced mammalian predators has altered the parental behaviour of the endemic New Zealand bellbird (Anthomis melanura). We examined parental behaviour of billbnirds at three woodlands sites in New Zealand that differed in predation risk: 1) a mainland site with exotic predators present (high predation risk), 2) a mainland site with exotic predators experimentally removed (low risk recently) and, 3) an off-shore island where exotic predators were never introduced (low risk always). We also compared parental behavior of bellbirds with two closely related Tasmanian honeyeaters (Phylidonyris spp) that evolved with native nest predators (high risk always). Increased nest predation risk has been postulated to favour reduced parental activity, and we tested whether island bellbirds responded to variation in predation risk. We found that females spent more time on the nest per incubating bout with increased risk of predation, a strategy that minimised activity at the nest during incubation. Parental activity during the nestling period, measured as number of feeding visits/hr, also decreased with increasing nest predation risk across sites, and was lowest among the honeyeaters in Tasmania that evolved with native predators. These results demonstrates that some island birds are able to respond to increased risk of predation by novel predators in ways that appear adaptive. We suggest that conservation efforts may be more effective if they take advantage of the ability of island birds to respond to novel predators, especially when the elimination of exotic predators is not possible.

  1. Predator Politics

    Directory of Open Access Journals (Sweden)

    Mary Louisa Cappelli

    2017-01-01

    Full Text Available Edward Abbey’s Desert Solitaire and Barbara Kingsolver’s Prodigal Summer urges readers to see coyotes as crucial members of the natural community whose predation is essential for the maintenance of biodiversity and ecological stability. Their cultural production provides a human story of ecocritical engagement for understanding the cascading effects of removing top predators from their ecosystems. By envisioning biocentric possibilities within place-based and scientific contexts, Edward Abbey and Barbara Kingsolver share a common theme of political ecology: political processes shape ecological conditions. A close reading of Edward Abbey’s Desert Solitaire and Barbara Kingsolver’s Prodigal Summer provides a literary entryway to connect research, arguments, and discourse across disciplines tasking readers to engage in political discussions of environmental sustainability and to consider viable solutions to preserve the ecological diversity of our predator populations and ecosystems.

  2. Bird species turnover is related to changing predation risk along a vegetation gradient

    Science.gov (United States)

    LaManna, Joseph A.; Hemenway, Amy B.; Boccadori, Vanna; Martin, Thomas E.

    2015-01-01

    Turnover in animal species along vegetation gradients is often assumed to reflect adaptive habitat preferences that are narrower than the full gradient. Specifically, animals may decline in abundance where their reproductive success is low, and these poor-quality locations differ among species. Yet habitat use does not always appear adaptive. The crucial tests of how abundances and demographic costs of animals vary along experimentally manipulated vegetation gradients are lacking. We examined habitat use and nest predation rates for 16 bird species that exhibited turnover with shifts in deciduous and coniferous vegetation. For most bird species, decreasing abundance was associated with increasing predation rates along both natural and experimentally modified vegetation gradients. This landscape-scale approach strongly supports the idea that vegetation-mediated effects of predation are associated with animal distributions and species turnover.

  3. Synchronised provisioning at the nest: parental coordination over care in a socially monogamous species.

    Science.gov (United States)

    van Rooij, Erica P; Griffith, Simon C

    2013-12-19

    Bi-parental care is very common in birds, occurring in over 90% of species, and is expected to evolve whenever the benefits of enhanced offspring survival exceed the costs to both parents of providing care. In altricial species, where the nestlings are entirely dependent on the parents for providing food until fledging, reproductive success is related to the capacity of the parents to provision the offspring at the nest. The degree to which parents synchronise their visits to the nest is rarely considered by studies of bi-parental care, and yet may be an important component of parental care, affecting the outcome of the reproductive attempt, and the dynamics of sexual conflict between the parents. Here we studied this aspect of parental care in the long-tailed finch (Poephila acuticauda), a socially monogamous estrildid finch. We monitored parental nest visit rates and the degree of parental visit synchrony, and assessed their effects on reproductive success (e.g., brood size, number of offspring fledged and nestling growth). The frequency of nest visits in a day was low in this species (nest visit synchrony may primarily be driven by the benefit of parents being together whilst foraging away from the nest, or may reduce nest predation by reducing the level of activity around the nest throughout the day.

  4. Effects of predation and dispersal on Mastomys natalensis population dynamics in Tanzanian maize fields

    DEFF Research Database (Denmark)

    Vibe-Petersen, Solveig; Leirs, Herwig; de Bruyn, L

    2006-01-01

    ), excluding predators by nets and attracting avian predators by nest boxes and perch poles. Because dispersal of the rodents could mask the predation pressure treatment effects, control and predator exclusion treatments were repeated with enclosed rodent populations. 3.  Population growth during the annual...... risk. Reducing dispersal of rodents removed the effect of predation on population growth and peak size, suggesting that local predators may play a role in driving rodent dispersal, but have otherwise little direct effect on population dynamics....

  5. Pasta Predation.

    Science.gov (United States)

    Waugh, Michael L.

    1986-01-01

    Presents a predator-prey simulation which involves students in collecting data, solving problems, and making predictions on the evolution of prey populations. Provides directives on how to perform the chi-square test and also includes an Applesoft BASK program that performs the calculations. (ML)

  6. Variation in clutch size in relation to nest size in birds

    NARCIS (Netherlands)

    Møller, Anders P.; Adriaensen, Frank; Artemyev, Alexandr; Bańbura, Jerzy; Barba, Emilio; Biard, Clotilde; Blondel, Jacques; Bouslama, Zihad; Bouvier, Jean-Charles; Camprodon, Jordi; Cecere, Francesco; Charmantier, Anne; Charter, Motti; Cichoń, Mariusz; Cusimano, Camillo; Czeszczewik, Dorota; Demeyrier, Virginie; Doligez, Blandine; Doutrelant, Claire; Dubiec, Anna; Eens, Marcel; Eeva, Tapio; Faivre, Bruno; Ferns, Peter N.; Forsman, Jukka T.; García-Del-Rey, Eduardo; Goldshtein, Aya; Goodenough, Anne E.; Gosler, Andrew G.; Góźdź, Iga; Grégoire, Arnaud; Gustafsson, Lars; Hartley, Ian R.; Heeb, Philipp; Hinsley, Shelley A.; Isenmann, Paul; Jacob, Staffan; Järvinen, Antero; Juškaitis, Rimvydas; Korpimäki, Erkki; Krams, Indrikis; Laaksonen, Toni; Leclercq, Bernard; Lehikoinen, Esa; Loukola, Olli; Lundberg, Arne; Mainwaring, Mark C.; Mänd, Raivo; Massa, Bruno; Mazgajski, Tomasz D.; Merino, Santiago; Mitrus, Cezary; Mönkkönen, Mikko; Morales-Fernaz, Judith; Morin, Xavier; Nager, Ruedi G.; Nilsson, Jan-Åke; Nilsson, Sven G.; Norte, Ana C.; Orell, Markku; Perret, Philippe; Pimentel, Carla S.; Pinxten, Rianne; Priedniece, Ilze; Quidoz, Marie-Claude; Remeš, Vladimir; Richner, Heinz; Robles, Hugo; Rytkönen, Seppo; Senar, Juan Carlos; Seppänen, Janne T.; da Silva, Luís P.; Slagsvold, Tore; Solonen, Tapio; Sorace, Alberto; Stenning, Martyn J.; Török, János; Tryjanowski, Piotr; van Noordwijk, Arie J.; von Numers, Mikael; Walankiewicz, Wiesław; Lambrechts, Marcel M.

    2014-01-01

    Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of

  7. Nesting of Morelet’s crocodile, Crocodylus moreletii (Dumeril and Bibron), in Los Tuxtlas, Mexico

    OpenAIRE

    A. Villegas; G. D. Mendoza; J. L. Arcos-García; V. H. Reynoso

    2017-01-01

    Abstract We evaluated the nesting by Crocodylus moreletii in Lago de Catemaco, Veracruz, southeastern, Mexico. During the nesting and hatching seasons, we searched for nests along the northern margins of the lake and small associated streams. We investigated egg mortality by weekly monitoring each of the nests found, recording sign of predation (tracks and holes dug into the nest) and the effect of water level fluctuations. We not found differences to nest between inland or flooded zones. How...

  8. Hawaii ESI: NESTS (Nest Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for seabird nesting colonies in coastal Hawaii. Vector points in this data set represent locations of...

  9. Maryland ESI: NESTS (Nest Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for raptors in Maryland. Vector points in this data set represent bird nesting sites. Species-specific...

  10. Louisiana ESI: NESTS (Nest Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for seabird and wading bird nesting colonies in coastal Louisiana. Vector points in this data set represent...

  11. Effects of seed density and proximity to refuge habitat on seed predation rates for a rare and a common Lupinus species.

    Science.gov (United States)

    Pardini, Eleanor A; Patten, Melissa V; Knight, Tiffany M

    2017-03-01

    Biotic interactions such as seed predation can play a role in explaining patterns of abundance among plant species. The effect of seed predation will depend on how the strength of predation differs across species and environments, and on the degree to which seed loss at one life-cycle phase increases fitness at another phase. Few studies have simultaneously quantified predispersal and postdispersal predation in co-occurring rare and common congeners, despite the value of estimating both for understanding causes of rarity. We quantified predispersal seed predation on the rare, herbaceous species Lupinus tidestromii (Fabaceae) and its common, shrubby congener L. chamissonis across multiple years in the same community. We experimentally measured postdispersal seed predation at two seed densities and locations near or far from an exotic grass housing high densities of deer mice ( Peromyscus maniculatus ), their primary, native seed predator. The common L. chamissonis had the lowest predispersal seed predation of the two lupine species, potentially because of its height: its high racemes received less predation than those low to the ground. By contrast, the same species experienced higher postdispersal seed predation, and at predators traveled long distances away from refuge habitat to consume their seeds. Across both plant species, mice preferentially predated high-density seed sources. Our results show differences in the magnitude and direction of seed predation between the species across different life-cycle phases. We demonstrated possible roles of proximity to refuge habitat, seed density, and seed size in these patterns. Congeneric comparisons would benefit from a comprehensive framework that considers seed predation across different life-cycle phases and the environmental context of predation. © 2017 Botanical Society of America.

  12. Weed seed predation in organic and conventional fields

    DEFF Research Database (Denmark)

    Navntoft, Søren; Wratten, S.D.; Kristensen, Kristian

    2009-01-01

    Enhanced biological control of weed seeds may improve sustainability of agricultural production. Biological control due to seed predation may be higher in organic fields because organic production generally supports more seed predators. To investigate such a difference, weed seed predation...... University and in two of the fields used for estimating seed predation. Recording of predators had therefore limited overlap with seed predation assays but was expected to give important information on key seed predators in the region. The mean seed removal rate was 17% in organic fields compared with 10...... edges. Overall, there was no consistent effect of distance from the field edge. Vegetation had a significant influence on the predation rates, with maximum rates at a medium-dense plant cover. Based on the video images, birds were the most important seed predators. The higher weed seed predation rate...

  13. Effectiveness of nest site restoration for the endangered northern map turtle : report 2 : use of artificial nesting sites and wildlife exclusion fences to enhance nesting success : research summary.

    Science.gov (United States)

    2016-10-01

    The Northern Map Turtle, is a state Endangered Species, found only in the : lower Susquehanna River in Maryland. The only area where nests of this : species are not heavily impacted by predators is in the town of Port Deposit. : However, turtles nest...

  14. Nesting Activity of Loggerhead Turtles (Caretta caretta at Göksu Delta, Turkey during 2004 and 2008 nesting seasons

    Directory of Open Access Journals (Sweden)

    Salih H. Durmus

    2011-07-01

    Full Text Available Göksu Delta is one of the most important nesting beaches in Turkey for the endangered loggerhead turtle (Caretta caretta. This paper provides information on the nesting activities of loggerhead turtles, the spatial and temporal distribution of nesting, nesting success, nesting density, hatching success, incubation duration and clutch size over two nesting seasons. A total of 902 emergences occurred over two seasons, of which 239 (26.5% nests were deposited (137 nests in 2004 and 102 nests in 2008 and the overall mean nesting density was 3.4 nests/km. The peak of nesting emergences takes place mainly in June. Of the overall nests, 226 (94.6% were excavated and 16044 eggs were counted. Of these eggs, 3680 (22.9% hatchlings emerged and 2695 (73.2% of hatchlings of them were able to reach the sea. The mean number of eggs per clutch was 71 (range: 15 – 143. The shortest and longest incubation duration in these 2 seasons ranged from 46 to 62 days with a mean of 53 days. The main problems are negatively affecting loggerhead turtle population at Göksu Delta are dense jackal predation both adult and eggs and inundation in nests. The average nesting effort here (mean: 119.5 nests/season confirms that Göksu Delta is one of the most important nesting sites for loggerhead turtles in Turkey.

  15. Using survival analysis of artificial and Real Brewer's sparrow (Spizella breweri breweri) nests to model site level and nest site factors associated with nest success in the South Okanagan region of Canada

    Science.gov (United States)

    Pam Krannitz Kym Welstead

    2005-01-01

    Predation is the predominant cause of nest failure for the Brewer's Sparrow (Spizella breweri breweri), a provincially red-listed shrub-steppe species that has experienced significant declines throughout most of its range. We monitored Brewer’s Sparrow nests and conducted an artificial nest experiment, in the South Okanagan Valley,...

  16. Conservation implications when the next predators are known. Chapter 2

    Science.gov (United States)

    Frank R., III Thompson; Christine A. Ribic

    2012-01-01

    Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using...

  17. Predator-induced changes in metabolism cannot explain the growth/predation risk tradeoff

    DEFF Research Database (Denmark)

    Steiner, Uli; Van Buskirk, Josh

    2009-01-01

    , consistent with the "fight-or-flight" response observed in many organisms. The long term reaction showed the opposite pattern: tadpoles reduced oxygen consumption after three weeks exposure to predators, which would act to reduce the growth cost of predator defence. The results point to an instantaneous...... and reversible stress response to predation risk. This suggests that the tradeoff between avoiding predators and growing rapidly is not caused by changes in metabolic rate, and must be sought in other behavioural or physiological processes....

  18. Usurpation of a Crowned Lapwing Vanellus coronatus nest by ...

    African Journals Online (AJOL)

    I report an instance of usurpation of a Crowned Lapwing Vanellus coronatus nest by a pair of African Wattled Lapwings Vanellus senegalensis. The nest, which originally contained a single Crowned Lapwing egg, eventually contained an additional three Wattled Lapwing eggs, before it was predated. Although parents of ...

  19. A new method for wireless video monitoring of bird nests

    Science.gov (United States)

    David I. King; Richard M. DeGraaf; Paul J. Champlin; Tracey B. Champlin

    2001-01-01

    Video monitoring of active bird nests is gaining popularity among researchers because it eliminates many of the biases associated with reliance on incidental observations of predation events or use of artificial nests, but the expense of video systems may be prohibitive. Also, the range and efficiency of current video monitoring systems may be limited by the need to...

  20. Regional Forest Fragmentation and the Nesting Success of Migratory Birds

    Science.gov (United States)

    Scott K. Robinson; Frank R. Thompson III; Therese M. Donovan; Donald R. Whitehead; John Faaborg

    1995-01-01

    Forest fragmentation, the disruption in the continuity of forest habitat, is hypothesized to be a major cause of population decline for, some species of forest birds because fragmentation reduces nesting (reproductive) success. Nest predation and parasitism by cowbirds increased with forest fragmentation in nine midwestern (United States)landscapes that varied from 6...

  1. Nesting of Morelet's crocodile, Crocodylus moreletii (Dumeril and Bibron), in Los Tuxtlas, Mexico.

    Science.gov (United States)

    Villegas, A; Mendoza, G D; Arcos-García, J L; Reynoso, V H

    2017-11-01

    We evaluated the nesting by Crocodylus moreletii in Lago de Catemaco, Veracruz, southeastern, Mexico. During the nesting and hatching seasons, we searched for nests along the northern margins of the lake and small associated streams. We investigated egg mortality by weekly monitoring each of the nests found, recording sign of predation (tracks and holes dug into the nest) and the effect of water level fluctuations. We not found differences to nest between inland or flooded zones. However, we found that egg size varied among nests. In nests built inland, predation was the major cause of egg mortality whereas flooding resulted in more deaths of eggs in the flooding zone. Flooding killed 25% of eggs monitored in this study. We suggest that to increase nest success in the Morelet's crocodile it is necessary to promote conservation of nesting areas around the lake, recently occupied by urban or tourist developments.

  2. Nesting of Morelet’s crocodile, Crocodylus moreletii (Dumeril and Bibron, in Los Tuxtlas, Mexico

    Directory of Open Access Journals (Sweden)

    A. Villegas

    2017-03-01

    Full Text Available Abstract We evaluated the nesting by Crocodylus moreletii in Lago de Catemaco, Veracruz, southeastern, Mexico. During the nesting and hatching seasons, we searched for nests along the northern margins of the lake and small associated streams. We investigated egg mortality by weekly monitoring each of the nests found, recording sign of predation (tracks and holes dug into the nest and the effect of water level fluctuations. We not found differences to nest between inland or flooded zones. However, we found that egg size varied among nests. In nests built inland, predation was the major cause of egg mortality whereas flooding resulted in more deaths of eggs in the flooding zone. Flooding killed 25% of eggs monitored in this study. We suggest that to increase nest success in the Morelet’s crocodile it is necessary to promote conservation of nesting areas around the lake, recently occupied by urban or tourist developments.

  3. Sexually selected nest-building--Pomatoschistus minutus males build smaller nest-openings in the presence of sneaker males.

    Science.gov (United States)

    Svensson, O; Kvarnemo, C

    2003-09-01

    Both natural selection and sexual selection may act on nest-building. We tested experimentally how different regimes of egg-predation and male-male competition influence nest-building before mating, using the marine fish sand goby, Pomatoschistus minutus. Males with sneaker males present built the smallest nest-openings, smaller than males held alone or with Pomatoschistus microps males (which may predate eggs and compete over nest-sites but not compete over fertilizations). Males with visual access to other nest-building males tended also to build smaller openings than males held alone or with P. microps. Males with egg-predators present built nests with openings not differing significantly from any other treatment. Our results indicate that the small nest-openings found in the sneaker male treatment are sexually selected through protection against sneaking or by female choice. Across treatments, time span before a male started to build his nest also explained variation in nest-opening width; males starting late built larger nest-openings.

  4. Partitioning mechanisms of predator interference in different habitats.

    Science.gov (United States)

    Griffen, Blaine D; Byers, James E

    2006-01-01

    Prey are often consumed by multiple predator species. Predation rates on shared prey species measured in isolation often do not combine additively due to interference or facilitation among the predator species. Furthermore, the strength of predator interactions and resulting prey mortality may change with habitat type. We experimentally examined predation on amphipods in rock and algal habitats by two species of intertidal crabs, Hemigrapsus sanguineus (top predators) and Carcinus maenas (intermediate predators). Algae provided a safer habitat for amphipods when they were exposed to only a single predator species. When both predator species were present, mortality of amphipods was less than additive in both habitats. However, amphipod mortality was reduced more in rock than algal habitat because intermediate predators were less protected in rock habitat and were increasingly targeted by omnivorous top predators. We found that prey mortality in general was reduced by (1) altered foraging behavior of intermediate predators in the presence of top predators, (2) top predators switching to foraging on intermediate predators rather than shared prey, and (3) density reduction of intermediate predators. The relative importance of these three mechanisms was the same in both habitats; however, the magnitude of each was greater in rock habitat. Our study demonstrates that the strength of specific mechanisms of interference between top and intermediate predators can be quantified but cautions that these results may be habitat specific.

  5. Invasive predators and global biodiversity loss.

    Science.gov (United States)

    Doherty, Tim S; Glen, Alistair S; Nimmo, Dale G; Ritchie, Euan G; Dickman, Chris R

    2016-10-04

    Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

  6. Effects of temperature and precipitation on grassland bird nesting success as mediated by patch size.

    Science.gov (United States)

    Zuckerberg, Benjamin; Ribic, Christine A; McCauley, Lisa A

    2018-02-06

    Grassland birds are declining faster than any other bird guild across North America. Shrinking ranges and population declines are attributed to widespread habitat loss and increasingly fragmented landscapes of agriculture and other land uses that are misaligned with grassland bird conservation. Concurrent with habitat loss and degradation, temperate grasslands have been disproportionally affected by climate change relative to most other terrestrial biomes. Distributions of grassland birds often correlate with gradients in climate, but few researchers have explored the consequences of weather on the demography of grassland birds inhabiting a range of grassland fragments. To do so, we modeled the effects of temperature and precipitation on nesting success rates of 12 grassland bird species inhabiting a range of grassland patches across North America (21,000 nests from 81 individual studies). Higher amounts of precipitation in the preceding year were associated with higher nesting success, but wetter conditions during the active breeding season reduced nesting success. Extremely cold or hot conditions during the early breeding season were associated with lower rates of nesting success. The direct and indirect influence of temperature and precipitation on nesting success was moderated by grassland patch size. The positive effects of precipitation in the preceding year on nesting success were strongest in relatively small grassland patches and had little effect in large patches. Conversely, warm temperatures reduced nesting success in small grassland patches but increased nesting success in large patches. Mechanisms underlying these differences may be patch-size-induced variation in microclimates and predator activity. Although the exact cause is unclear, large grassland patches, the most common metric of grassland conservation, appears to moderate the effects of weather on grassland-bird demography and could be an effective component of climate-change adaptation.

  7. Modeling nest survival of cavity-nesting birds in relation to postfire salvage logging

    Science.gov (United States)

    Vicki Saab; Robin E. Russell; Jay Rotella; Jonathan G. Dudley

    2011-01-01

    Salvage logging practices in recently burned forests often have direct effects on species associated with dead trees, particularly cavity-nesting birds. As such, evaluation of postfire management practices on nest survival rates of cavity nesters is necessary for determining conservation strategies. We monitored 1,797 nests of 6 cavity-nesting bird species: Lewis'...

  8. Spawning chronology, nest site selection and nest success of smallmouth bass during benign streamflow conditions

    Science.gov (United States)

    Dauwalter, D.C.; Fisher, W.L.

    2007-01-01

    We documented the nesting chronology, nest site selection and nest success of smallmouth bass Micropterus dolomieu in an upstream (4th order) and downstream (5th order) reach of Baron Fork Creek, Oklahoma. Males started nesting in mid-Apr. when water temperatures increased to 16.9 C upstream, and in late-Apr. when temperatures increased to 16.2 C downstream. Streamflows were low (77% upstream to 82% downstream of mean Apr. streamflow, and 12 and 18% of meanjun. streamflow; 47 and 55 y of record), and decreased throughout the spawning period. Larger males nested first upstream, as has been observed in other populations, but not downstream. Upstream, progeny in 62 of 153 nests developed to swim-up stage. Downstream, progeny in 31 of 73 nests developed to swim-up. Nesting densities upstream (147/km) and downstream (100/km) were both higher than any densities previously reported. Males selected nest sites with intermediate water depths, low water velocity and near cover, behavior that is typical of smallmouth bass. Documented nest failures resulted from human disturbance, angling, and longear sunfish predation. Logistic exposure models showed that water velocity at the nest was negatively related and length of the guarding male was positively related to nest success upstream. Male length and number of degree days were both positively related to nest success downstream. Our results, and those of other studies, suggest that biological factors account for most nest failures during benign (stable, low flow) streamflow conditions, whereas nest failures attributed to substrate mobility or nest abandonment dominate when harsh streamflow conditions (spring floods) coincide with the spawning season.

  9. Predator recognition in rainbowfish, Melanotaenia duboulayi, embryos.

    Directory of Open Access Journals (Sweden)

    Lois Jane Oulton

    Full Text Available Exposure to olfactory cues during embryonic development can have long term impacts on birds and amphibians behaviour. Despite the vast literature on predator recognition and responses in fishes, few researchers have determined how fish embryos respond to predator cues. Here we exposed four-day-old rainbowfish (Melanotaenia duboulayi embryos to cues emanating from a novel predator, a native predator and injured conspecifics. Their response was assessed by monitoring heart rate and hatch time. Results showed that embryos have an innate capacity to differentiate between cues as illustrated by faster heart rates relative to controls. The greatest increase in heart rate occurred in response to native predator odour. While we found no significant change in the time taken for eggs to hatch, all treatments experienced slight delays as expected if embryos are attempting to reduce exposure to larval predators.

  10. Nest-site selection in the acorn woodpecker

    Science.gov (United States)

    Hooge, P.N.; Stanback, M.T.; Koenig, Walter D.

    1999-01-01

    Acorn Woodpeckers (Melanerpes formicivorus) at Hastings Reservation in central California prefer to nest in dead limbs in large, dead valley oaks (Quercus lobata) and California sycamores (Platanus racemosa) that are also frequently used as acorn storage trees. Based on 232 nest cavities used over an 18-year period, we tested whether preferred or modal nest-site characters were associated with increased reproductive success (the "nest-site quality" hypothesis). We also examined whether more successful nests were likely to experience more favorable microclimatic conditions or to be less accessible to terrestrial predators. We found only equivocal support for the nest-site quality hypothesis: only 1 of 5 preferred characters and 2 of 10 characters exhibiting a clear modality were correlated with higher reproductive success. All three characteristics of nests known or likely to be associated with a more favorable microclimate, and two of five characteristics likely to render nests less accessible to predators, were correlated with higher reproductive success. These results suggest that nest cavities in this population are built in part to take advantage of favorable microclimatic conditions and, to a lesser extent, to reduce access to predators. However, despite benefits of particular nest characteristics, birds frequently nested in apparently suboptimal cavities. We also found a significant relationship between mean group size and the history of occupancy of particular territories and the probability of nest cavities being built in microclimatically favorable live limbs, suggesting that larger groups residing on more stable territories were better able to construct nests with optimal characteristics. This indicates that there may be demographic, as well as ecological, constraints on nest-site selection in this primary cavity nester.

  11. The design and function of birds' nests.

    Science.gov (United States)

    Mainwaring, Mark C; Hartley, Ian R; Lambrechts, Marcel M; Deeming, D Charles

    2014-10-01

    All birds construct nests in which to lay eggs and/or raise offspring. Traditionally, it was thought that natural selection and the requirement to minimize the risk of predation determined the design of completed nests. However, it is becoming increasingly apparent that sexual selection also influences nest design. This is an important development as while species such as bowerbirds build structures that are extended phenotypic signals whose sole purpose is to attract a mate, nests contain eggs and/or offspring, thereby suggesting a direct trade-off between the conflicting requirements of natural and sexual selection. Nest design also varies adaptively in order to both minimize the detrimental effects of parasites and to create a suitable microclimate for parents and developing offspring in relation to predictable variation in environmental conditions. Our understanding of the design and function of birds' nests has increased considerably in recent years, and the evidence suggests that nests have four nonmutually exclusive functions. Consequently, we conclude that the design of birds' nests is far more sophisticated than previously realized and that nests are multifunctional structures that have important fitness consequences for the builder/s.

  12. The design and function of birds' nests

    Science.gov (United States)

    Mainwaring, Mark C; Hartley, Ian R; Lambrechts, Marcel M; Deeming, D Charles

    2014-01-01

    All birds construct nests in which to lay eggs and/or raise offspring. Traditionally, it was thought that natural selection and the requirement to minimize the risk of predation determined the design of completed nests. However, it is becoming increasingly apparent that sexual selection also influences nest design. This is an important development as while species such as bowerbirds build structures that are extended phenotypic signals whose sole purpose is to attract a mate, nests contain eggs and/or offspring, thereby suggesting a direct trade-off between the conflicting requirements of natural and sexual selection. Nest design also varies adaptively in order to both minimize the detrimental effects of parasites and to create a suitable microclimate for parents and developing offspring in relation to predictable variation in environmental conditions. Our understanding of the design and function of birds' nests has increased considerably in recent years, and the evidence suggests that nests have four nonmutually exclusive functions. Consequently, we conclude that the design of birds' nests is far more sophisticated than previously realized and that nests are multifunctional structures that have important fitness consequences for the builder/s. PMID:25505520

  13. Determine movement patterns and survival rates of Central Valley Chinook salmon, steelhead and their predators using acoustic tags.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The project’s objective is to document movement patterns and survival rates of Chinook salmon, steelhead, green sturgeon, and other fish from several sources in...

  14. The increased risk of predation enhances cooperation

    Science.gov (United States)

    Krams, Indrikis; Bērziņš, Arnis; Krama, Tatjana; Wheatcroft, David; Igaune, Kristīne; Rantala, Markus J.

    2010-01-01

    Theory predicts that animals in adverse conditions can decrease individual risks and increase long-term benefits by cooperating with neighbours. However, some empirical studies suggest that animals often focus on short-term benefits, which can reduce the likelihood that they will cooperate with others. In this experimental study, we tested between these two alternatives by evaluating whether increased predation risk (as a correlate of environmental adversity) enhances or diminishes the occurrence of cooperation in mobbing, a common anti-predator behaviour, among breeding pied flycatchers Ficedula hypoleuca. We tested whether birds would join their mobbing neighbours more often and harass a stuffed predator placed near their neighbours' nests more intensely in areas with a higher perceived risk of predation. Our results show that birds attended mobs initiated by their neighbours more often, approached the stuffed predator significantly more closely, and mobbed it at a higher intensity in areas where the perceived risk of predation was experimentally increased. In such high-risk areas, birds also were more often involved in between-pair cooperation. This study demonstrates the positive impact of predation risk on cooperation in breeding songbirds, which might help in explaining the emergence and evolution of cooperation. PMID:19846454

  15. Predator effects on reef fish settlement depend on predator origin and recruit density.

    Science.gov (United States)

    Benkwitt, Cassandra E

    2017-04-01

    During major life-history transitions, animals often experience high mortality rates due to predation, making predator avoidance particularly advantageous during these times. There is mixed evidence from a limited number of studies, however, regarding how predator presence influences settlement of coral-reef fishes and it is unknown how other potentially mediating factors, including predator origin (native vs. nonnative) or interactions among conspecific recruits, mediate the non-consumptive effects of predators on reef fish settlement. During a field experiment in the Caribbean, approximately 52% fewer mahogany snapper (Lutjanus mahogoni) recruited to reefs with a native predator (graysby grouper, Cephalopholis cruentata) than to predator-free control reefs and reefs with an invasive predator (red lionfish, Pterois volitans) regardless of predator diet. These results suggest that snapper recruits do not recognize nonnative lionfish as a threat. However, these effects depended on the density of conspecific recruits, with evidence that competition may limit the response of snapper to even native predators at the highest recruit densities. In contrast, there was no effect of predator presence or conspecific density on the recruitment of bicolor damselfish (Stegastes partitus). These context-dependent responses of coral-reef fishes to predators during settlement may influence individual survival and shape subsequent population and community dynamics. © 2017 by the Ecological Society of America.

  16. Effects of nest density, location, and timing on breeding success of Caspian Terns

    Science.gov (United States)

    Antolos, Michelle; Roby, D.D.; Lyons, Donald E.; Anderson, Scott K.; Collis, K.

    2006-01-01

    One of the proposed benefits of colonial nesting in birds is the protection afforded against avian predators. This advantage may be counter-balanced by the negative effects of intraspecific aggression on breeding success. Effects of nest density, nest location within the colony, and timing of nest initiation on productivity of Caspian Terns (Sterna caspia) were investigated on Crescent Island in the mid-Columbia River, Washington, USA. In the absence of intense nest predation at the Crescent Island tern colony, it was hypothesized that nest density would be negatively associated with productivity. A rangefinder was used to determine spatial distribution of Caspian Tern nests, and these data used to calculate nest characteristics (nest density, nearest neighbor distance, and distance to colony edge) for a randomly-selected subset of nests monitored for nest chronology and productivity. Productivity did not differ between nests in high- and low-density areas of the colony, and was positively associated with earlier nest initiation. Early nests were more productive, were located in areas of higher nest density, and were further from the colony edge than late nests. The strong effect of timing may have been attributable to seasonal declines in prey resources for terns at this site. Our results suggest that Caspian Terns nesting at the highest densities observed in this study did not incur immediate reproductive costs, despite increased potential for encounters between chicks and aggressive conspecific adults.

  17. The nest as fortress: Defensive behavior of Polybia emaciata, a mud-nesting eusocial wasp

    Directory of Open Access Journals (Sweden)

    Sean O'Donnell

    2002-02-01

    Full Text Available The swarm-founding wasp Polybia emaciata is unusual among eusocial Vespidae because it uses mud, rather than wood pulp, as its primary nest construction material. Polybia emaciata nests are more durable than similarly sized paper nests. We tested the hypothesis that the defensive behavior of this wasp may have been modified to take advantage of their strong nests in defense against vertebrate attacks. We simulated vertebrate disturbances by tapping on, and breathing in, P. emaciata. nests and similarly sized P. occidentalis paper nests in the same location at the same time. Polybia emaciata. responses to disturbance were qualitatively different from those of P. occidentalis. The latter exit the nest and attack, while P. emaciata. workers typically fled or entered the nest, attacking only after repeated and extended disturbances. We conclude that durable nest material may permit predator avoidance behavior in P. emaciata.. We compare the defensive responses of P. emaciata. workers with those of other swarm-founding Vespidae, and discuss several selective forces that could cause the evolution of species variation in nest defense behavior.

  18. Can cat predation help competitors coexist in seabird communities?

    Science.gov (United States)

    Pontier, Dominique; Fouchet, David; Bried, Joël

    2010-01-07

    On oceanic islands, nest site availability can be an important factor regulating seabird population dynamics. The potential for birds to secure a nest to reproduce can be an important component of their life histories. The dates at which different seabird species arrive at colonies to breed will have important consequences for their relative chances of success. Early arrival on the island allows birds to obtain nests more easily and have higher reproductive success. However, the presence of an introduced predator may reverse this situation. For instance, in the sub-Antarctic Kerguelen archipelago, early arriving birds suffer heavy predation from introduced cats. Cats progressively switch from seabirds to rabbits, since the local rabbit population starts to peak after early arriving seabird species have already returned to the colony. When late-arriving birds arrive, cat predation pressure on seabirds is thus weaker. In this paper, we investigate the assumption that the advantage of early nest mnopolization conferred to early arriving birds may be counterbalanced by the cost resulting from predation. We develop a mathematical model representing a simplified situation in which two insular seabird species differ only in their arrival date at the colony site and compete for nesting sites. We conclude that predation may ensure the coexistence of the two bird species or favor the late-arriving species, but only when seasonal variations in predation pressure are large. Interestingly, we conclude that arriving early is only favorable until a given level where high reproductive success no longer compensates for the long exposure to strong predation pressure. Our work suggests that predation can help to maintain the balance between species of different phenologies.

  19. Living with aliens: effects of invasive shrub honeysuckles on avian nesting.

    Directory of Open Access Journals (Sweden)

    Jason M Gleditsch

    Full Text Available Invasive species have come to the forefront of conservation biology as a major threat to native biodiversity. Habitats dominated by shrub honeysuckles (Lonicera spp. in the United States have been characterized as "ecological traps" by ecologists. Here we tested this hypothesis by investigating the effects of shrub honeysuckles on the nesting ecology of native birds in seven study sites in central Pennsylvania, USA. We examined how the abundance of shrub honeysuckles influenced the selection of nesting substrates and habitat for a community of common songbirds, and the parental-care behavior and nestling development of gray catbirds (Dumetella carolinensis. We found that birds had a strong bias towards nesting in honeysuckle shrubs, but not necessarily for nesting in honeysuckle-dominated habitats. Nest predation rates were affected by the density of nests in a habitat, but not by the overall abundance of honeysuckles in such habitats. Honeysuckle abundance in the habitat did show significant effects on some parental-care behavioral parameters: catbirds had higher nest visitation rates and shorter visit lengths in areas of high honeysuckle density. On average, Gray catbirds fed fruit 12%±0.31 s.e. of their nestling-feeding bouts, mostly fruits of shrub honeysuckles. Nestlings in sites with high honeysuckle density also showed higher mass:tarsus ratios, suggesting a good (possibly better physiological condition of catbird nestlings at the time of fledging. Our study shows that honeysuckle-dominated habitats could have equivocal effects on nesting parameters of common species of native birds. We advise more caution in the widespread denomination of novel plant communities with high densities of honeysuckle as "ecological traps" as effects can be null or positive on native birds in certain localities.

  20. Invasive rats strengthen predation pressure on bird eggs in a South Pacific island rainforest.

    Science.gov (United States)

    Duron, Quiterie; Bourguet, Edouard; De Meringo, Hélène; Millon, Alexandre; Vidal, Eric

    2017-12-01

    Invasive rats ( Rattus spp.) are known to have pervasive impacts on island birds, particularly on their nesting success. To conserve or restore bird populations, numerous invasive rat control or eradication projects are undertaken on islands worldwide. However, such projects represent a huge investment and the decision-making process requires proper assessment of rat impacts. Here, we assessed the influence of two sympatric invasive rats ( Rattus rattus and R. exulans ) on native bird eggs in a New Caledonian rainforest, using artificial bird-nest monitoring. A total of 178 artificial nests containing two eggs of three different sizes were placed either on the ground or 1.5 m high and monitored at the start of the birds' breeding season. Overall, 12.4% of the nests were depredated during the first 7 days. At site 1, where nests were monitored during 16 days, 41.8% of the nests were depredated. The main predator was the native crow Corvus moneduloides , responsible for 62.9% of the overall predation events. Rats were responsible for only 22.9% of the events, and ate only small and medium eggs at both heights. Our experiment suggests that in New Caledonia, predation pressure by rats strengthens overall bird-nest predation, adding to that by native predators. Experimental rat control operations may allow reduced predation pressure on nests as well as the recording of biodiversity responses after rat population reduction.

  1. Effectiveness of nest site restoration for the endangered northern map turtle. Report no. 1 : nest site selection and nest success from 2013-2014 and establishment of environmental center : [research summary].

    Science.gov (United States)

    2015-05-01

    The Northern Map Turtle, Graptemys geographica, is a Maryland state : Endangered Species, found only in the lower Susquehanna River in Maryland. : The only area where nests of this species are not heavily impacted by predators : occurs in the town of...

  2. Predation efficiency of Anopheles gambiae larvae by aquatic predators in western Kenya highlands

    Directory of Open Access Journals (Sweden)

    Nyindo Mramba

    2011-07-01

    Full Text Available Abstract Background The current status of insecticide resistance in mosquitoes and the effects of insecticides on non-target insect species have raised the need for alternative control methods for malaria vectors. Predation has been suggested as one of the important regulation mechanisms for malaria vectors in long-lasting aquatic habitats, but the predation efficiency of the potential predators is largely unknown in the highlands of western Kenya. In the current study, we examined the predation efficiency of five predators on Anopheles gambiae s.s larvae in 24 hour and semi- field evaluations. Methods Predators were collected from natural habitats and starved for 12 hours prior to starting experiments. Preliminary experiments were conducted to ascertain the larval stage most predated by each predator species. When each larval instar was subjected to predation, third instar larvae were predated at the highest rate. Third instar larvae of An. gambiae were introduced into artificial habitats with and without refugia at various larval densities. The numbers of surviving larvae were counted after 24 hours in 24. In semi-field experiments, the larvae were counted daily until they were all either consumed or had developed to the pupal stage. Polymerase chain reaction was used to confirm the presence of An. gambiae DNA in predator guts. Results Experiments found that habitat type (P P P P An. gambiae DNA was found in at least three out of ten midguts for all predator species. Gambusia affins was the most efficient, being three times more efficient than tadpoles. Conclusion These experiments provide insight into the efficiency of specific natural predators against mosquito larvae. These naturally occurring predators may be useful in biocontrol strategies for aquatic stage An. gambiae mosquitoes. Further investigations should be done in complex natural habitats for these predators.

  3. Satellite telemetry reveals higher fishing mortality rates than previously estimated, suggesting overfishing of an apex marine predator.

    Science.gov (United States)

    Byrne, Michael E; Cortés, Enric; Vaudo, Jeremy J; Harvey, Guy C McN; Sampson, Mark; Wetherbee, Bradley M; Shivji, Mahmood

    2017-08-16

    Overfishing is a primary cause of population declines for many shark species of conservation concern. However, means of obtaining information on fishery interactions and mortality, necessary for the development of successful conservation strategies, are often fisheries-dependent and of questionable quality for many species of commercially exploited pelagic sharks. We used satellite telemetry as a fisheries-independent tool to document fisheries interactions, and quantify fishing mortality of the highly migratory shortfin mako shark ( Isurus oxyrinchus ) in the western North Atlantic Ocean. Forty satellite-tagged shortfin mako sharks tracked over 3 years entered the Exclusive Economic Zones of 19 countries and were harvested in fisheries of five countries, with 30% of tagged sharks harvested. Our tagging-derived estimates of instantaneous fishing mortality rates ( F = 0.19-0.56) were 10-fold higher than previous estimates from fisheries-dependent data (approx. 0.015-0.024), suggesting data used in stock assessments may considerably underestimate fishing mortality. Additionally, our estimates of F were greater than those associated with maximum sustainable yield, suggesting a state of overfishing. This information has direct application to evaluations of stock status and for effective management of populations, and thus satellite tagging studies have potential to provide more accurate estimates of fishing mortality and survival than traditional fisheries-dependent methodology. © 2017 The Author(s).

  4. Arctic foxes, lemmings, and canada goose nest survival at cape Churchill, Manitoba

    Science.gov (United States)

    Reiter, M.E.; Andersen, D.E.

    2011-01-01

    We examined factors influencing Canada Goose (Branta canadensis interior) annual nest success, including the relative abundance of collared lemmings (Dicrostonyx richardsoni), arctic fox (Alopex lagopus) den occupancy, nest density, and spring phenology using data collected during annual Canada Goose breeding area surveys at Cape Churchill, Manitoba. Nest density and arctic fox den occupancy strongly influenced Canada Goose nest success. High nest density resulted in higher nest success and high den occupancy reduced nest success. Nest success was not influenced by lemming abundance in the current or previous year as predicted by the "bird-lemming" hypothesis. Reducing arctic fox abundance through targeted management increased nest survival of Canada Geese; a result that further emphasizes the importance of arctic fox as nest predators in this system. The spatial distribution of nest predators, at least for dispersed-nesting geese, may be most important for nest survival, regardless of the abundance of small mammals in the local ecosystem. Further understanding of the factors influencing the magnitude and variance in arctic fox abundance in this region, and the spatial scale at which these factors are realized, is necessary to fully explain predator-prey-alternative prey dynamics in this system. ?? 2011 by the Wilson Ornithological Society.

  5. Synchronised provisioning at the nest: parental coordination over care in a socially monogamous species

    Directory of Open Access Journals (Sweden)

    Erica P. van Rooij

    2013-12-01

    Full Text Available Bi-parental care is very common in birds, occurring in over 90% of species, and is expected to evolve whenever the benefits of enhanced offspring survival exceed the costs to both parents of providing care. In altricial species, where the nestlings are entirely dependent on the parents for providing food until fledging, reproductive success is related to the capacity of the parents to provision the offspring at the nest. The degree to which parents synchronise their visits to the nest is rarely considered by studies of bi-parental care, and yet may be an important component of parental care, affecting the outcome of the reproductive attempt, and the dynamics of sexual conflict between the parents. Here we studied this aspect of parental care in the long-tailed finch (Poephila acuticauda, a socially monogamous estrildid finch. We monitored parental nest visit rates and the degree of parental visit synchrony, and assessed their effects on reproductive success (e.g., brood size, number of offspring fledged and nestling growth.The frequency of nest visits in a day was low in this species (<1 visit/h, but there was a high level of synchrony by the two partners with 73% of visits made together. There was a correlation between the proportion of visits that were made by the pair together and the size of the brood at hatching, although it was not related to the number of fledglings a pair produced, or the quality of those offspring. We suggest that nest visit synchrony may primarily be driven by the benefit of parents being together whilst foraging away from the nest, or may reduce nest predation by reducing the level of activity around the nest throughout the day.

  6. Avian predation on juvenile salmonids in the Lower Columbia River; 1998 annual report

    International Nuclear Information System (INIS)

    Collis, Ken; Adamany, Stephanie; Roby, Daniel D.; Craig, David P.; Lyons, Donald E.

    2000-01-01

    The authors initiated a field study in 1997 to assess the impacts of fish-eating colonial waterbirds (i.e., terns, cormorants, and gulls) on the survival of juvenile salmonids in the lower Columbia River. Here the authors present results from the 1998 breeding season, the second field season of work on this project. The research objectives in 1998 were to: (1) determine the location, size, nesting chronology, nesting success, and population trajectories of breeding colonies of fish-eating birds in the lower Columbia River; (2) determine diet composition of fish-eating birds, including taxonomic composition and energy content of various prey types; (3) estimate forage fish consumption rates, with special emphasis on juvenile salmonids, by breeding adults and their young; (4) determine the relative vulnerability of different groups of juvenile salmonids to bird predation; (5) identify foraging range, foraging strategies, and habitat utilization by piscivorous waterbirds; and (6) test the feasibility of various alternative methods for managing avian predation on juvenile salmonids and develop recommendations to reduce avian predation, if warranted by the results

  7. Avian Predation on Juvenile Salmonids in the Lower Columbia River: 1998 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Collis, Ken; Adamany, Stephanie; Roby, Daniel D.; Craig, David P.; Lyons, Donald E.

    2000-04-01

    The authors initiated a field study in 1997 to assess the impacts of fish-eating colonial waterbirds (i.e., terns, cormorants, and gulls) on the survival of juvenile salmonids in the lower Columbia River. Here the authors present results from the 1998 breeding season, the second field season of work on this project. The research objectives in 1998 were to: (1) determine the location, size, nesting chronology, nesting success, and population trajectories of breeding colonies of fish-eating birds in the lower Columbia River; (2) determine diet composition of fish-eating birds, including taxonomic composition and energy content of various prey types; (3) estimate forage fish consumption rates, with special emphasis on juvenile salmonids, by breeding adults and their young; (4) determine the relative vulnerability of different groups of juvenile salmonids to bird predation; (5) identify foraging range, foraging strategies, and habitat utilization by piscivorous waterbirds; and (6) test the feasibility of various alternative methods for managing avian predation on juvenile salmonids and develop recommendations to reduce avian predation, if warranted by the results.

  8. Effects of land-use change and rainfall in Sudano-Sahelian West Africa on the diet and nestling growth rates of an avian predator

    NARCIS (Netherlands)

    Buij, R.; Folkertsma, I.; Kortekaas, K.; longh, De H.H.; Komdeur, J.

    2013-01-01

    Raptor populations in Sudano-Sahelian West Africa are being severely affected by widespread habitat alteration which depletes prey populations, potentially aggravated by changing rainfall patterns. We studied Grasshopper Buzzards Butastur rufipennis at nests in natural and transformed habitats in

  9. Effects of land-use change and rainfall in Sudano-Sahelian West Africa on the diet and nestling growth rates of an avian predator

    NARCIS (Netherlands)

    Buij, Ralph; Folkertsma, Ingrid; Kortekaas, Kim; De Iongh, Hans H.; Komdeur, Jan; Sergio, Fabrizio

    Raptor populations in Sudano-Sahelian West Africa are being severely affected by widespread habitat alteration which depletes prey populations, potentially aggravated by changing rainfall patterns. We studied Grasshopper Buzzards Butastur rufipennis at nests in natural and transformed habitats in

  10. Nesting ecology of Townsend's warblers in relation to habitat characteristics in a mature boreal forest

    Science.gov (United States)

    Matsuoka, S.M.; Handel, Colleen M.; Roby, D.D.

    1997-01-01

    We investigated the nesting ecology of Townsend's Warblers (Dendroica townsendi) from 1993-1995 in an unfragmented boreal forest along the lower slopes of the Chugach Mountains in southcentral Alaska. We examined habitat characteristics of nest sites in relation to factors influencing reproductive success. Almost all territory-holding males (98%, n = 40) were successful in acquiring mates. Nest success was 54% (n = 24 nests), with nest survivorship greater during incubation (87%) than during the nestling period (62%). Most nesting failure (80%) was attributable to predation, which occurred primarily during the nestling period. Fifty-five percent of nests containing nestling were infested with the larvae of bird blow-flies (Protocalliphora braueri and P. spenceri), obligatory blood-feeding parasites. The combined effects of Protocalliphora infestation and inclement weather apparently resulted in nestling mortality in 4 of the 24 nests. Nests that escaped predation were placed in white spruce with larger diameter than those lost to predation: nests that escaped blow-fly parasitism were located higher in nest trees and in areas with lower densities of woody shrubs than those that were infested. The availability of potential nest sites with these key features may be important in determining reproductive success in Townsend's Warblers.

  11. Breeding of the plain-mantled tit-spintail (Leptasthenura aegithaloides in a variable hawk (Geranoaetus polyosoma nest in the Atacama Desert, Chile

    Directory of Open Access Journals (Sweden)

    Patrich Cerpa

    2016-04-01

    Full Text Available A strategy to avoid nest predation by various bird species is the selection of inaccessible sites or sites of actual danger for potential predators. In this sense nesting near a top predator may be an effective strategy to avoid nest predation, if this predator does not have a preference for eggs or nestlings of the first species. This note reports the first record of nesting by Plain-mantled Tit-Spinetail (Leptasthenura aegithaloides Kittlitz, 1830 in an active nest of the variable Hawk (Geranoaetus polyosoma Quoy & Gaimard, 1824 and the nesting of the common diuca-finch (Diuca diuca Molina, 1782 nearby, during two consecutive years, in the Atacama Desert, Chile. This occurred during the “flowering desert” phenomenon in October of 2014 and September of 2015. We discuss hypotheses that may explain this biological association and its possible ecological implications.

  12. Trait-mediated trophic cascade creates enemy-free space for nesting hummingbirds.

    Science.gov (United States)

    Greeney, Harold F; Meneses, M Rocio; Hamilton, Chris E; Lichter-Marck, Eli; Mannan, R William; Snyder, Noel; Snyder, Helen; Wethington, Susan M; Dyer, Lee A

    2015-09-01

    The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades. Although birds are important predators in terrestrial ecosystems, clear examples of trait-mediated indirect effects involving bird predators have almost never been documented. Such indirect effects are important for structuring ecological communities and are likely to be negatively impacted by habitat fragmentation, climate change, and other factors that reduce abundance of top predators. We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks. An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

  13. Predation and caribou populations

    Directory of Open Access Journals (Sweden)

    Dale R. Seip

    1991-10-01

    Full Text Available Predation, especially wolf (Canis lupus predation, limits many North American caribou (Rangifer tarandus populations below the density that food resources could sustain. The impact of predation depends on the parameters for the functional and numerical response of the wolves, relative to the potential annual increment of the caribou population. Differences in predator-avoidance strategies largely explain the major differences in caribou densities that occur naturally in North America. Caribou migrations that spatially separate caribou from wolves allow relatively high densities of caribou to survive. Non-migratory caribou that live in areas where wolf populations are sustained by alternate prey can be eliminated by wolf predation.

  14. Decoration Increases the Conspicuousness of Raptor Nests.

    Science.gov (United States)

    Canal, David; Mulero-Pázmány, Margarita; Negro, Juan José; Sergio, Fabrizio

    2016-01-01

    Avian nests are frequently concealed or camouflaged, but a number of species builds noticeable nests or use conspicuous materials for nest decoration. In most cases, nest decoration has a role in mate choice or provides thermoregulatory or antiparasitic benefits. In territorial species however, decorations may serve additional or complementary functions, such as extended phenotypic signaling of nest-site occupancy and social status to potential intruders. The latter may benefit both signaler and receiver by minimizing the risk of aggressive interactions, especially in organisms with dangerous weaponry. Support for this hypothesis was recently found in a population of black kites (Milvus migrans), a territorial raptor that decorates its nest with white artificial materials. However, the crucial assumption that nest decorations increased nest-site visibility to conspecifics was not assessed, a key aspect given that black kite nests may be well concealed within the canopy. Here, we used an unmanned aircraft system to take pictures of black kite nests, with and without an experimentally placed decoration, from different altitudes and distances simulating the perspective of a flying and approaching, prospecting intruder. The pictures were shown to human volunteers through a standardized routine to determine whether detection rates varied according the nest decoration status and distance. Decorated nests consistently showed a higher detection frequency and a lower detection-latency, compared to undecorated versions of the same nests. Our results confirm that nest decoration in this species may act as a signaling medium that enhances nest visibility for aerial receivers, even at large distances. This finding complements previous work on this communication system, which showed that nest decoration was a threat informing trespassing conspecifics on the social dominance, territory quality and fighting capabilities of the signaler.

  15. Predation on rose galls: parasitoids and predators determine gall size through directional selection.

    Directory of Open Access Journals (Sweden)

    Zoltán László

    Full Text Available Both predators and parasitoids can have significant effects on species' life history traits, such as longevity or clutch size. In the case of gall inducers, sporadically there is evidence to suggest that both vertebrate predation and insect parasitoid attack may shape the optimal gall size. While the effects of parasitoids have been studied in detail, the influence of vertebrate predation is less well-investigated. To better understand this aspect of gall size evolution, we studied vertebrate predation on galls of Diplolepis rosae on rose (Rosa canina shrubs. We measured predation frequency, predation incidence, and predation rate in a large-scale observational field study, as well as an experimental field study. Our combined results suggest that, similarly to parasitoids, vertebrate predation makes a considerable contribution to mortality of gall inducer larvae. On the other hand, its influence on gall size is in direct contrast to the effect of parasitoids, as frequency of vertebrate predation increases with gall size. This suggests that the balance between predation and parasitoid attack shapes the optimal size of D. rosae galls.

  16. Where to nest? Ecological determinants of chimpanzee nest abundance and distribution at the habitat and tree species scale.

    Science.gov (United States)

    Carvalho, Joana S; Meyer, Christoph F J; Vicente, Luis; Marques, Tiago A

    2015-02-01

    Conversion of forests to anthropogenic land-uses increasingly subjects chimpanzee populations to habitat changes and concomitant alterations in the plant resources available to them for nesting and feeding. Based on nest count surveys conducted during the dry season, we investigated nest tree species selection and the effect of vegetation attributes on nest abundance of the western chimpanzee, Pan troglodytes verus, at Lagoas de Cufada Natural Park (LCNP), Guinea-Bissau, a forest-savannah mosaic widely disturbed by humans. Further, we assessed patterns of nest height distribution to determine support for the anti-predator hypothesis. A zero-altered generalized linear mixed model showed that nest abundance was negatively related to floristic diversity (exponential form of the Shannon index) and positively with the availability of smaller-sized trees, reflecting characteristics of dense-canopy forest. A positive correlation between nest abundance and floristic richness (number of plant species) and composition indicated that species-rich open habitats are also important in nest site selection. Restricting this analysis to feeding trees, nest abundance was again positively associated with the availability of smaller-sized trees, further supporting the preference for nesting in food tree species from dense forest. Nest tree species selection was non-random, and oil palms were used at a much lower proportion (10%) than previously reported from other study sites in forest-savannah mosaics. While this study suggests that human disturbance may underlie the exclusive arboreal nesting at LCNP, better quantitative data are needed to determine to what extent the construction of elevated nests is in fact a response to predators able to climb trees. Given the importance of LCNP as refuge for Pan t. verus our findings can improve conservation decisions for the management of this important umbrella species as well as its remaining suitable habitats. © 2014 Wiley Periodicals, Inc.

  17. Variation in nesting behavior of eight species of spider mites, Stigmaeopsis having sociality

    Science.gov (United States)

    Saito, Yutaka; Zhang, Yan-Xuan; Mori, Kotaro; Ito, Katsura; Sato, Yukie; Chittenden, Anthony R.; Lin, Jian-Zhen; Chae, Younghae; Sakagami, Takane; Sahara, Ken

    2016-10-01

    Nesting behavior is considered to be an important element of social living in animals. The spider mites belonging to the genus Stigmaeopsis spend their lives within nests produced from silk threads. Several of these species show cooperative sociality, while the others are subsocial. In order to identify the origins of this social behavior, comparisons of nest sizes, nesting behaviors (making nests continuously or separately), and their associated traits (fecal deposition patterns) were made for eight cogeneric Stigmaeopsis species showing various levels of social development. All of these species inhabit bamboo plants (Poaceae). We initially addressed the proximate factor of nest size variation. The variation in nest size of the eight species corresponded well with the variation in dorsal seta sc1 length, suggesting that nest size variation among species may have a genetic basis. The time spent within a nest (nest duration) increased with nest size on the respective host plants. Nest arrangement patterns varied among species showing different sized nests: Large nest builders continuously extended their nests, while middle and small nest-building species built new separate nests, which resulted in different social interaction times among species, and is thought to be closely related to social development. Fecal deposition behaviors also varied among Stigmaeopsis species, suggesting diversity in anti-predatory adaptations. Finally, we discuss how the variation in sociality observed within this genus is likely the result of nest size variation that initially evolved as anti-predator strategies.

  18. Artificial Cavities and Nest Site Selection by Puerto Rican Parrots: a Multiscale Assessment

    Directory of Open Access Journals (Sweden)

    Thomas H. White, Jr.

    2006-12-01

    Full Text Available We examined nest site selection by Puerto Rican Parrots, a secondary cavity nester, at several spatial scales using the nest entrance as the central focal point relative to 20 habitat and spatial variables. The Puerto Rican Parrot is unique in that, since 2001, all known nesting in the wild has occurred in artificial cavities, which also provided us with an opportunity to evaluate nest site selection without confounding effects of the actual nest cavity characteristics. Because of the data limitations imposed by the small population size of this critically endangered endemic species, we employed a distribution-free statistical simulation approach to assess site selection relative to characteristics of used and unused nesting sites. Nest sites selected by Puerto Rican Parrots were characterized by greater horizontal and vertical visibility from the nest entrance, greater density of mature sierra palms, and a more westerly and leeward orientation of nest entrances than unused sites. Our results suggest that nest site selection in this species is an adaptive response to predation pressure, to which the parrots respond by selecting nest sites offering advantages in predator detection and avoidance at all stages of the nesting cycle. We conclude that identifying and replicating the “nest gestalt” of successful nesting sites may facilitate conservation efforts for this and other endangered avian species.

  19. Male Rock Sparrow (Petronia petronia) Nest Defence Correlates with Female Ornament Size

    DEFF Research Database (Denmark)

    Griggio, Matteo; Matessi, Giuliano; Pilastro, Andrea

    2003-01-01

    We investigated the relationship between male nest defence and female breast patch size in an alpine population of rock sparrow (Petronia petronia) in northern Italy. We presented a mounted weasel (Mustela nivalis), a common nest predator, to 28 pairs breeding in nest boxes, with 12-13-d-old nest......We investigated the relationship between male nest defence and female breast patch size in an alpine population of rock sparrow (Petronia petronia) in northern Italy. We presented a mounted weasel (Mustela nivalis), a common nest predator, to 28 pairs breeding in nest boxes, with 12-13-d...... defence factor was significantly related only to female breast patch size. We argue that male rock sparrows apparently make parental investment decisions according to their mate's quality, and examine possible alternative hypotheses....

  20. Effectiveness of nest site restoration for the endangered northern map turtle : report 2 : use of artificial nesting sites and wildlife exclusion fence to enhance nesting success.

    Science.gov (United States)

    2016-10-01

    The Northern Map Turtle, Graptemys geographica, is a Maryland state endangered species, found only in the lower Susquehanna River in Maryland. The only area where nests of this species are not heavily impacted by predators occurs in the town of Port ...

  1. Rats and seabirds: effects of egg size on predation risk and the potential of conditioned taste aversion as a mitigation method.

    Science.gov (United States)

    Latorre, Lucía; Larrinaga, Asier R; Santamaría, Luis

    2013-01-01

    Seabirds nesting on islands are threatened by invasive rodents, such as mice and rats, which may attack eggs, chicks and even adults. The low feasibility of rat eradications on many islands makes the development of alternate control plans necessary. We used a combination of field experiments on a Mediterranean island invaded by black rats (Rattusrattus) to evaluate (1) the predation risk posed to different-sized seabird eggs and (2), the potential of two deterrent methods (electronic and chemical) to reduce its impact. Rats were able to consume eggs of all sizes (12 to 68 g), but survival increased 13 times from the smallest to the largest eggs (which also had more resistant eggshells). Extrapolation to seabird eggs suggests that the smallest species (Hydrobatespelagicus) suffer the most severe predation risk, but even the largest (Larusmichahellis) could suffer >60% mortality. Nest attack was not reduced by the deterrents. However, chemical deterrence (conditioned taste aversion by lithium chloride) slowed the increase in predation rate over time, which resulted in a three-fold increase in egg survival to predation as compared to both control and electronic deterrence. At the end of the experimental period, this effect was confirmed by a treatment swap, which showed that conferred protection remains at least 15 days after cessation of the treatment. Results indicate that small seabird species are likely to suffer severe rates of nest predation by rats and that conditioned taste aversion, but not electronic repellents, may represent a suitable method to protect colonies when eradication or control is not feasible or cost-effective.

  2. Texas ratsnake predation on southern flying squirrels in red-cockaded woodpecker cavities

    Science.gov (United States)

    D. Craig Rudolph; Richard R. Schaefer; Josh B. Pierce; Dan Saenz; Richard N. Conner

    2009-01-01

    Elaphe spp. (ratsnakes) are frequent predators on cavity-nesting birds and other vertebrates, including Glaucomys volans (Southern Flying Squirrels). They are known predators of Picoides borealis (Red-cockaded Woodpeckers), especially during the nestling phase. Picoides borealis cavities are frequently occupied by Southern Flying Squirrels, often several squirrels per...

  3. Coexistence for an Almost Periodic Predator-Prey Model with Intermittent Predation Driven by Discontinuous Prey Dispersal

    Directory of Open Access Journals (Sweden)

    Yantao Luo

    2017-01-01

    Full Text Available An almost periodic predator-prey model with intermittent predation and prey discontinuous dispersal is studied in this paper, which differs from the classical continuous and impulsive dispersal predator-prey models. The intermittent predation behavior of the predator species only happens in the channels between two patches where the discontinuous migration movement of the prey species occurs. Using analytic approaches and comparison theorems of the impulsive differential equations, sufficient criteria on the boundedness, permanence, and coexistence for this system are established. Finally, numerical simulations demonstrate that, for an intermittent predator-prey model, both the intermittent predation and intrinsic growth rates of the prey and predator species can greatly impact the permanence, extinction, and coexistence of the population.

  4. Comparative reproductive biology of sympatric species: Nest and chick survival of American avocets and black-necked stilts

    Science.gov (United States)

    Ackerman, Joshua T.; Herzog, Mark P.; Takekawa, John Y.; Hartman, Christopher A.

    2014-01-01

    Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black-necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio-marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro-habitats likely reduced stilt chick’s vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co-occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

  5. Selective Predation of a Stalking Predator on Ungulate Prey.

    Directory of Open Access Journals (Sweden)

    Marco Heurich

    Full Text Available Prey selection is a key factor shaping animal populations and evolutionary dynamics. An optimal forager should target prey that offers the highest benefits in terms of energy content at the lowest costs. Predators are therefore expected to select for prey of optimal size. Stalking predators do not pursue their prey long, which may lead to a more random choice of prey individuals. Due to difficulties in assessing the composition of available prey populations, data on prey selection of stalking carnivores are still scarce. We show how the stalking predator Eurasian lynx (Lynx lynx selects prey individuals based on species identity, age, sex and individual behaviour. To address the difficulties in assessing prey population structure, we confirm inferred selection patterns by using two independent data sets: (1 data of 387 documented kills of radio-collared lynx were compared to the prey population structure retrieved from systematic camera trapping using Manly's standardized selection ratio alpha and (2 data on 120 radio-collared roe deer were analysed using a Cox proportional hazards model. Among the larger red deer prey, lynx selected against adult males-the largest and potentially most dangerous prey individuals. In roe deer lynx preyed selectively on males and did not select for a specific age class. Activity during high risk periods reduced the risk of falling victim to a lynx attack. Our results suggest that the stalking predator lynx actively selects for size, while prey behaviour induces selection by encounter and stalking success rates.

  6. Survival during the Breeding Season: Nest Stage, Parental Sex, and Season Advancement Affect Reed Warbler Survival.

    Directory of Open Access Journals (Sweden)

    Kaja Wierucka

    Full Text Available Avian annual survival has received much attention, yet little is known about seasonal patterns in survival, especially of migratory passerines. In order to evaluate survival rates and timing of mortality within the breeding season of adult reed warblers (Acrocephalus scirpaceus, mark-recapture data were collected in southwest Poland, between 2006 and 2012. A total of 612 individuals (304 females and 308 males were monitored throughout the entire breeding season, and their capture-recapture histories were used to model survival rates. Males showed higher survival during the breeding season (0.985, 95% CI: 0.941-0.996 than females (0.869, 95% CI: 0.727-0.937. Survival rates of females declined with the progression of the breeding season (from May to August, while males showed constant survival during this period. We also found a clear pattern within the female (but not male nesting cycle: survival was significantly lower during the laying, incubation, and nestling periods (0.934, 95% CI: 0.898-0.958, when birds spent much time on the nest, compared to the nest building and fledgling periods (1.000, 95% CI: 1.00-1.000, when we did not record any female mortality. These data (coupled with some direct evidence, like bird corpses or blood remains found next to/on the nest may suggest that the main cause of adult mortality was on-nest predation. The calculated survival rates for both sexes during the breeding season were high compared to annual rates reported for this species, suggesting that a majority of mortality occurs at other times of the year, during migration or wintering. These results have implications for understanding survival variation within the reproductive period as well as general trends of avian mortality.

  7. Predators indirectly control vector-borne disease: linking predator-prey and host-pathogen models.

    Science.gov (United States)

    Moore, Sean M; Borer, Elizabeth T; Hosseini, Parviez R

    2010-01-06

    Pathogens transmitted by arthropod vectors are common in human populations, agricultural systems and natural communities. Transmission of these vector-borne pathogens depends on the population dynamics of the vector species as well as its interactions with other species within the community. In particular, predation may be sufficient to control pathogen prevalence indirectly via the vector. To examine the indirect effect of predators on vectored-pathogen dynamics, we developed a theoretical model that integrates predator-prey and host-pathogen theory. We used this model to determine whether predation can prevent pathogen persistence or alter the stability of host-pathogen dynamics. We found that, in the absence of predation, pathogen prevalence in the host increases with vector fecundity, whereas predation on the vector causes pathogen prevalence to decline, or even become extinct, with increasing vector fecundity. We also found that predation on a vector may drastically slow the initial spread of a pathogen. The predator can increase host abundance indirectly by reducing or eliminating infection in the host population. These results highlight the importance of studying interactions that, within the greater community, may alter our predictions when studying disease dynamics. From an applied perspective, these results also suggest situations where an introduced predator or the natural enemies of a vector may slow the rate of spread of an emerging vector-borne pathogen.

  8. Species invasion shifts the importance of predator dependence.

    Science.gov (United States)

    Griffen, Blaine D; Delaney, David G

    2007-12-01

    The strength of interference between foraging individuals can influence per capita consumption rates, with important consequences for predator and prey populations and system stability. Here we demonstrate how the replacement of a previously established invader, the predatory crab Carcinus maenas, by the recently invading predatory crab Hemigrapsus sanguineus shifts predation from a species that experiences strong predator interference (strong predator dependence) to one that experiences weak predator interference (weak predator dependence). We demonstrate using field experiments that differences in the strength of predator dependence persist for these species both when they forage on a single focal prey species only (the mussel Mytilus edulis) and when they forage more broadly across the entire prey community. This shift in predator dependence with species replacement may be altering the biomass across trophic levels, consistent with theoretical predictions, as we show that H. sanguineus populations are much larger than C. maenas populations throughout their invaded ranges. Our study highlights that predator dependence may differ among predator species and demonstrates that different predatory impacts of two conspicuous invasive predators may be explained at least in part by different strengths of predator dependence.

  9. Predator confusion is sufficient to evolve swarming behaviour.

    Science.gov (United States)

    Olson, Randal S; Hintze, Arend; Dyer, Fred C; Knoester, David B; Adami, Christoph

    2013-08-06

    Swarming behaviours in animals have been extensively studied owing to their implications for the evolution of cooperation, social cognition and predator-prey dynamics. An important goal of these studies is discerning which evolutionary pressures favour the formation of swarms. One hypothesis is that swarms arise because the presence of multiple moving prey in swarms causes confusion for attacking predators, but it remains unclear how important this selective force is. Using an evolutionary model of a predator-prey system, we show that predator confusion provides a sufficient selection pressure to evolve swarming behaviour in prey. Furthermore, we demonstrate that the evolutionary effect of predator confusion on prey could in turn exert pressure on the structure of the predator's visual field, favouring the frontally oriented, high-resolution visual systems commonly observed in predators that feed on swarming animals. Finally, we provide evidence that when prey evolve swarming in response to predator confusion, there is a change in the shape of the functional response curve describing the predator's consumption rate as prey density increases. Thus, we show that a relatively simple perceptual constraint--predator confusion--could have pervasive evolutionary effects on prey behaviour, predator sensory mechanisms and the ecological interactions between predators and prey.

  10. Behavior at a nest of Amazilia lactea (Aves, Trochilidae

    Directory of Open Access Journals (Sweden)

    Yoshika Oniki

    2000-11-01

    Full Text Available The hummingbird Amazilia lactea (Lesson, 1832 built a nest in São Paulo, Brazil, in the spring (Oct and added lichens during incubation. The female incubated over 70 per cent of the day, 1-56 min per visit, and brooded two small young somewhat less; brooding stopped by about 10 days of age, as did night brooding. Lack of night brooding for large young hummingbirds may reflect lack of space in a small nest. Young stayed in the nest 19 days. Feedings were widely spaced, and presence of possible predators caused alarm.

  11. Nest niche dynamics of Meyer's Parrot Poicephalus meyeri in the ...

    African Journals Online (AJOL)

    Meyer's Parrot Poicephalus meyeri is the only cavity-nesting bird species that breeds during winter in the Okavango Delta. This is facilitated by exclusive access to arthropod larvae incubating inside and feeding on fruits and pods in their diet. To minimise predation risk and overcome low overnight temperatures they have ...

  12. Predation threats to the Red-billed Tropicbird breeding colony of Saba: focus on cats

    NARCIS (Netherlands)

    Debrot, A.O.; Ruijter, M.; Endarwin, W.; Hooft, van P.; Wulf, K.

    2014-01-01

    Feral domestic cats (Felis catus) are recognized as one of the most devastating alien predator species in the world and are a major threat to nesting colonies of the Red-billed Tropicbird (Phaethon aethereus), on Saba island, Dutch Caribbean. Cats and rats are both known to impact nesting seabirds

  13. Construction of arboreal nests by brown-nosed coatis, Nasua nasua (Carnivora: Procyonidae in the Brazilian Pantanal

    Directory of Open Access Journals (Sweden)

    Natalie Olifiers

    2009-09-01

    Full Text Available The construction of arboreal nests is rare among mammals in the order Carnivora. However, coatis (Procyonidae: Nasua Storr, 1780 build arboreal nests that are used for resting or birthing. Here we describe Nasua nasua (Linnaeus, 1766 nests located during a telemetry study of coatis in the Brazilian Pantanal. Coati nests were all "bird-like", that is, open nests having a semispherical shape. Nests were constructed of twigs, branches, and lianas sometimes interlaced with leaves. Nest volume was 30-50 cm³ and average nest height was approximately 9.5 m. Nests were found in open "cerrado" vegetation, along forest edges, or in interior "cordilheiras" forest. The reasons why coatis build such nests are unclear, but may relate to inter or intraspecific competition for nesting sites, litter size, thermoregulation, and predation avoidance.

  14. Nest site selection and breeding success in three Turdus thrush species coexisting in an urban environment

    Czech Academy of Sciences Publication Activity Database

    Mikula, P.; Hromada, M.; Albrecht, Tomáš; Tryjanowski, P.

    2014-01-01

    Roč. 49, č. 1 (2014), s. 83-92 ISSN 0001-6454 Institutional support: RVO:68081766 Keywords : breeding success * coexistence * nest-habitat partitioning * nest site selection * predation * synurbization * urban habitat * thrushes Subject RIV: EG - Zoology Impact factor: 0.745, year: 2014

  15. Effect of landscape matrix type on nesting ecology of the Northern Cardinal

    Science.gov (United States)

    R.A. Sargent; J.C. Kilgo; B.R. Chapman; K.V. Miller

    2015-01-01

    Spatial distribution of forests relative to other habitats in a landscape may influence nest success of songbirds. For example, nest predation in mature forests increases as the percentage of clear-cut land in the surrounding matrix increases (Yahner and Scott 1988). Blake and Karr (1987) noted that birds breeding in forest fragments may incorporate adjacent habitats,...

  16. Habitat edges have weak effects on duck nest survival at local spatial scales

    Science.gov (United States)

    Raquel, Amelia J; Ringelman, Kevin M.; Ackerman, Joshua T.; Eadie, John M.

    2015-01-01

    Edge effects on nesting success have been documented in breeding birds in a variety of contexts, but there is still uncertainty in how edge type and spatial scale determine the magnitude and detectability of edge effects. Habitat edges are often viewed as predator corridors that surround or penetrate core habitat and increase the risk of predation for nearby nests. We studied the effects of three different types of potential predator corridors (main perimeter roads, field boundaries, and ATV trails within fields) on waterfowl nest survival in California. We measured the distance from duck nests to the nearest edge of each type, and used distance as a covariate in a logistic exposure analysis of nest survival. We found only weak evidence for edge effects due to predation. The best supported model of nest survival included all three distance categories, and while all coefficient estimates were positive (indicating that survival increased with distance from edge), 85% coefficient confidence intervals approached or bounded zero indicating an overall weak effect of habitat edges on nest success. We suggest that given the configuration of edges at our site, there may be few areas far enough from hard edges to be considered ‘core’ habitat, making edge effects on nest survival particularly difficult to detect.

  17. Effect of nest characteristics on thermal properties, clutch size, and reproductive performance for an open-cup nesting songbird

    Science.gov (United States)

    Michael E. Akresh; Daniel R. Ardia; David I. King

    2017-01-01

    Maintaining avian eggs and young at optimum temperatures for development can increase hatching success and nestling condition, but this maintenance requires parental energetic demands. Bird nests, which often provide a structure to safely hold the eggs and nestlings and protect them from predators, can additionally be designed to help maintain eggs' optimum...

  18. Cavity Nesting Birds

    Science.gov (United States)

    Virgil E. Scott; Keith E. Evans; David R. Patton; Charles P. Stone

    1977-01-01

    Many species of cavity-nesting birds have declined because of habitat reduction. In the eastern United States, where primeval forests are gone, purple martins depend almost entirely on man-made nesting structures (Allen and Nice 1952). The hole-nesting population of peregrine falcons disappeared with the felling of the giant trees upon which they depended (Hickey and...

  19. Predator-induced changes in metabolism cannot explain the growth/predation risk tradeoff.

    Directory of Open Access Journals (Sweden)

    Ulrich K Steiner

    2009-07-01

    Full Text Available Defence against predators is usually accompanied by declining rates of growth or development. The classical growth/predation risk tradeoff assumes reduced activity as the cause of these declines. However, in many cases these costs cannot be explained by reduced foraging effort or enhanced allocation to defensive structures under predation risk. Here, we tested for a physiological origin of defence costs by measuring oxygen consumption in tadpoles (Rana temporaria exposed to predation risk over short and long periods of time. The short term reaction was an increase in oxygen consumption, consistent with the "fight-or-flight" response observed in many organisms. The long term reaction showed the opposite pattern: tadpoles reduced oxygen consumption after three weeks exposure to predators, which would act to reduce the growth cost of predator defence. The results point to an instantaneous and reversible stress response to predation risk. This suggests that the tradeoff between avoiding predators and growing rapidly is not caused by changes in metabolic rate, and must be sought in other behavioural or physiological processes.

  20. Predator Presence and Vegetation Density Affect Capture Rates and Detectability of Litoria aurea Tadpoles: Wide-Ranging Implications for a Common Survey Technique.

    Directory of Open Access Journals (Sweden)

    Madeleine R Sanders

    Full Text Available Trapping is a common sampling technique used to estimate fundamental population metrics of animal species such as abundance, survival and distribution. However, capture success for any trapping method can be heavily influenced by individuals' behavioural plasticity, which in turn affects the accuracy of any population estimates derived from the data. Funnel trapping is one of the most common methods for sampling aquatic vertebrates, although, apart from fish studies, almost nothing is known about the effects of behavioural plasticity on trapping success. We used a full factorial experiment to investigate the effects that two common environmental parameters (predator presence and vegetation density have on the trapping success of tadpoles. We estimated that the odds of tadpoles being captured in traps was 4.3 times higher when predators were absent compared to present and 2.1 times higher when vegetation density was high compared to low, using odds ratios based on fitted model means. The odds of tadpoles being detected in traps were also 2.9 times higher in predator-free environments. These results indicate that common environmental factors can trigger behavioural plasticity in tadpoles that biases trapping success. We issue a warning to researchers and surveyors that trapping biases may be commonplace when conducting surveys such as these, and urge caution in interpreting data without consideration of important environmental factors present in the study system. Left unconsidered, trapping biases in capture success have the potential to lead to incorrect interpretations of data sets, and misdirection of limited resources for managing species.

  1. Species diversity modulates predation

    NARCIS (Netherlands)

    Kratina, P.; Vos, M.; Anholt, B.R.

    2007-01-01

    Predation occurs in a context defined by both prey and non-prey species. At present it is largely unknown how species diversity in general, and species that are not included in a predator's diet in particular, modify predator–prey interactions.Therefore we studied how both the density and diversity

  2. Variation in clutch size in relation to nest size in birds.

    Science.gov (United States)

    Møller, Anders P; Adriaensen, Frank; Artemyev, Alexandr; Bańbura, Jerzy; Barba, Emilio; Biard, Clotilde; Blondel, Jacques; Bouslama, Zihad; Bouvier, Jean-Charles; Camprodon, Jordi; Cecere, Francesco; Charmantier, Anne; Charter, Motti; Cichoń, Mariusz; Cusimano, Camillo; Czeszczewik, Dorota; Demeyrier, Virginie; Doligez, Blandine; Doutrelant, Claire; Dubiec, Anna; Eens, Marcel; Eeva, Tapio; Faivre, Bruno; Ferns, Peter N; Forsman, Jukka T; García-Del-Rey, Eduardo; Goldshtein, Aya; Goodenough, Anne E; Gosler, Andrew G; Góźdź, Iga; Grégoire, Arnaud; Gustafsson, Lars; Hartley, Ian R; Heeb, Philipp; Hinsley, Shelley A; Isenmann, Paul; Jacob, Staffan; Järvinen, Antero; Juškaitis, Rimvydas; Korpimäki, Erkki; Krams, Indrikis; Laaksonen, Toni; Leclercq, Bernard; Lehikoinen, Esa; Loukola, Olli; Lundberg, Arne; Mainwaring, Mark C; Mänd, Raivo; Massa, Bruno; Mazgajski, Tomasz D; Merino, Santiago; Mitrus, Cezary; Mönkkönen, Mikko; Morales-Fernaz, Judith; Morin, Xavier; Nager, Ruedi G; Nilsson, Jan-Åke; Nilsson, Sven G; Norte, Ana C; Orell, Markku; Perret, Philippe; Pimentel, Carla S; Pinxten, Rianne; Priedniece, Ilze; Quidoz, Marie-Claude; Remeš, Vladimir; Richner, Heinz; Robles, Hugo; Rytkönen, Seppo; Senar, Juan Carlos; Seppänen, Janne T; da Silva, Luís P; Slagsvold, Tore; Solonen, Tapio; Sorace, Alberto; Stenning, Martyn J; Török, János; Tryjanowski, Piotr; van Noordwijk, Arie J; von Numers, Mikael; Walankiewicz, Wiesław; Lambrechts, Marcel M

    2014-09-01

    Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nests of 21 species of hole and non-hole-nesting birds. There was a significant, positive relationship between clutch size and the base area of the nest box or the nest, and this relationship did not differ significantly between open nesting and hole-nesting species. The slope of the relationship showed significant intraspecific and interspecific heterogeneity among four species of secondary hole-nesting species, but also among all 116 slope estimates. The estimated relationship between clutch size and nest box base area in study sites with more than a single size of nest box was not significantly different from the relationship using studies with only a single size of nest box. The slope of the relationship between clutch size and nest base area in different species of birds was significantly negatively related to minimum base area, and less so to maximum base area in a given study. These findings are consistent with the hypothesis that bird species have a general reaction norm reflecting the relationship between nest size and clutch size. Further, they suggest that scientists may influence the clutch size decisions of hole-nesting birds through the provisioning of nest boxes of varying sizes.

  3. Columbia River ESI: NESTS (Nest Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for bird nesting sites in the Columbia River area. Vector points in this data set represent locations of...

  4. Research, Monitoring, and Evaluation of Avian Predation on Salmonid Smolts in the Lower and Mid-Columbia River, 2008 Draft Season Summary.

    Energy Technology Data Exchange (ETDEWEB)

    Roby, Daniel D. [USGS - Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University; Collis, Ken [Real Time Research, Inc.; Lyons, Donald E. [USGS - Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University

    2009-07-08

    This report describes investigations into predation by piscivorous colonial waterbirds on juvenile salmonids (Oncorhynchus spp.) from throughout the Columbia River basin during 2008. East Sand Island in the Columbia River estuary again supported the largest known breeding colony of Caspian terns (Hydroprogne caspia) in the world (approximately 10,700 breeding pairs) and the largest breeding colony of double-crested cormorants (Phalacrocorax auritus) in western North America (approximately 10,950 breeding pairs). The Caspian tern colony increased from 2007, but not significantly so, while the double-crested cormorant colony experienced a significant decline (20%) from 2007. Average cormorant nesting success in 2008, however, was down only slightly from 2007, suggesting that food supply during the 2008 nesting season was not the principal cause of the decline in cormorant colony size. Total consumption of juvenile salmonids by East Sand Island Caspian terns in 2008 was approximately 6.7 million smolts (95% c.i. = 5.8-7.5 million). Caspian terns nesting on East Sand Island continued to rely primarily on marine forage fishes as a food supply. Based on smolt PIT tag recoveries on the East Sand Island Caspian tern colony, predation rates were highest on steelhead in 2008; minimum predation rates on steelhead smolts detected passing Bonneville Dam averaged 8.3% for wild smolts and 10.7% for hatchery-raised smolts. In 2007, total smolt consumption by East Sand Island double-crested cormorants was about 9.2 million juvenile salmonids (95% c.i. = 4.4-14.0 million), similar to or greater than that of East Sand Island Caspian terns during that year (5.5 million juvenile salmonids; 95% c.i. = 4.8-6.2 million). The numbers of smolt PIT tags recovered on the cormorant colony in 2008 were roughly proportional to the relative availability of PIT-tagged salmonids released in the Basin, suggesting that cormorant predation on salmonid smolts in the estuary was less selective than tern

  5. Reduced flocking by birds on islands with relaxed predation.

    Science.gov (United States)

    Beauchamp, Guy

    2004-05-22

    Adaptive hypotheses for the evolution of flocking in birds have usually focused on predation avoidance or foraging enhancement. It still remains unclear to what extent each factor has contributed to the evolution of flocking. If predation avoidance were the sole factor involved, flocking should not be prevalent when predation is relaxed. I examined flocking tendencies along with mean and maximum flock size in species living on islands where predation risk is either absent or negligible and then compared these results with matched counterparts on the mainland. The dataset consisted of 46 pairs of species from 22 different islands across the world. The tendency to flock was retained on islands in most species, but in pairs with dissimilar flocking tendencies, island species were less likely to flock. Mean and maximum flock size were smaller on islands than on the mainland. Potential confounding factors such as population density, nest predation, habitat type, food type and body mass failed to account for the results. The results suggest that predation is a significant factor in the evolution of flocking in birds. Nevertheless, predation and other factors, such as foraging enhancement, probably act together to maintain the trait in most species.

  6. Predation on seabirds by red foxes at Shaiak Island, Alaska

    Science.gov (United States)

    Petersen, M.R.

    1982-01-01

    Two Red Foxes (Vulpes fulva) that invaded Shaiak Island before the 1976 nesting season had a marked impact on the nesting success of five of seven species of seabirds breeding on the island that year. Common Eiders (Somateria mollissima), Glaucous-winged Gulls (Larus glaucescens), and Common Murres (Uria aalge), that nest in areas accessible to foxes, did not raise any young to fledging. Double-crested Cormorants (Phalacrocorax auritus) were only slightly more successful; 13 (4.3%) of 300 pairs raised one or more young to fledging. Evidence suggested that 21 (35.6%) of 62 pairs of Tufted Puffins (Lunda cirrhata) lost eggs or chicks to foxes, and foxes killed at least 13 (8.3%) of 156 adult puffins on ten sample plots. Conversely, Black-Legged Kittiwakes (Rissa tridactyla) and Pelagic Cormorants (Phalacrocorax pelagicus), which nested primarily on cliffs inaccessible to foxes, lost very few nests. There was no apparent change in general nest site selections by seabirds the following year, when foxes were no longer present. Any avoidance by birds of areas vulnerable to fox predation would probably be discernible only after several years of continuous predation.

  7. Large increase in nest size linked to climate change: an indicator of life history, senescence and condition.

    Science.gov (United States)

    Møller, Anders Pape; Nielsen, Jan Tøttrup

    2015-11-01

    Many animals build extravagant nests that exceed the size required for successful reproduction. Large nests may signal the parenting ability of nest builders suggesting that nests may have a signaling function. In particular, many raptors build very large nests for their body size. We studied nest size in the goshawk Accipiter gentilis, which is a top predator throughout most of the Nearctic. Both males and females build nests, and males provision their females and offspring with food. Nest volume in the goshawk is almost three-fold larger than predicted from their body size. Nest size in the goshawk is highly variable and may reach more than 600 kg for a bird that weighs ca. 1 kg. While 8.5% of nests fell down, smaller nests fell down more often than large nests. There was a hump-shaped relationship between nest volume and female age, with a decline in nest volume late in life, as expected for senescence. Clutch size increased with nest volume. Nest volume increased during 1977-2014 in an accelerating fashion, linked to increasing spring temperature during April, when goshawks build and start reproduction. These findings are consistent with nest size being a reliable signal of parental ability, with large nest size signaling superior parenting ability and senescence, and also indicating climate warming.

  8. Snowpack and variation in reproductive ecology of a montane ground-nesting passerine, Junco hyemalis

    Science.gov (United States)

    Smith, Kimberly G.; Andersen, Douglas C.

    1985-01-01

    Effects of snow depth and rate of snowmelt on reproduction of a montane ground-nesting passerine were examined in a 5-year study of Dark-eyed Juncos Junco hyemalis in northern Utah, USA. Distribution of clucth sizes differed significantly among years. Although most clutches contained four eggs, 3-egg clutches, due primarily to second nestings, were more common during a year of early snowmelt and 5-egg clutches were most common during two years of late snowmelt. Average clutch size was lowest in an early snowmelt year and average clutch size and date at which meadows became snow-free were significantly positively correlated. Average hatching date of 4-egg clutches was also significantly positively correlated with date at which meadows became snow-free demonstrating that most birds tracked the pattern of snowmelt. Early snowmelt may allow more pairs to attempt second nesting, but late-lying snow causes breeding to be delayed, allowing time for only one nesting attempt. During this delay, female juncos continue to feed and some may gain enough reserves to produce larger clutches, accounting for the increase in average clutch size in years of late snowmelt. Three female juncos examined in June 1982, a period of late snowmelt, had significantly more lipid reserves than did six males collected at the same time, suggesting that females are not physiologically stressed while awaiting snowmelt. By tracking snowmelt patterns, juncos synchronize production of young with peak summer insect abundance and potentially decrease risk of predation. Snow depth and rate of snowmelt are thus proximate environmental factors that may influence the reproductive ecology of ground-nesting passerines.

  9. Nest-site Selection of the Greater Painted Snipe (Rostratula benghalensis benghalensis in Fallow Fields of I-Lan, Taiwan

    Directory of Open Access Journals (Sweden)

    Yu-Hsun Hsu

    2011-09-01

    Full Text Available Nest site quality often affects nest success and the fitness of avian breeders. Vegetation structure and water depth are possible factors evaluated in nest-site selection by ground nesting birds in wetlands. Vegetation structure may affect the predation risk, and water depth is linked to the possibility of being flooded. We examined these two factors in the nest site selection of a wetland bird, the Greater Painted Snipe (Rostratula benghalensis benghalensis, in I-Lan, Taiwan. We found 17 Greater Painted Snipe nests in wet fallow fields. By paired comparisons, we found the breeders tended to nest on sites with higher vegetation coverage and lower water depth than random sites. No significant difference was found in the vegetation height between the nest sites and the paired random sites. Five nests failed to hatch due to flooding or predation. The preference for nest sites with low water depth may be an effort to avoid being flooded and the preference for dense vegetation coverage at nest sites may be a response to predation risk.

  10. Nest site selection by Hypsiboas faber(Anura, Hylidae in Southern Brazil

    Directory of Open Access Journals (Sweden)

    André L. Luza

    2015-12-01

    Full Text Available ABSTRACT Male gladiator frogs of Hypsiboas Wagler, 1830 build nests on available substrate surrounding ponds and streams where female spawn eggs during the breeding period. Although gladiator frogs seem to show plasticity in the way they construct their nests, there is no study reporting if these species present preferences about microhabitat conditions for nest-building (mainly under subtropical climate. Predation pressure and environmental conditions have been considered major processes shaping the great diversity of reproductive strategies performed by amphibians, but microhabitat conditions should explain where to build a nest as well as how nest looks. This study aimed to test nest site selection for nest-building by Hypsiboas faber(Wied-Neuwied, 1821, determining which factors are related to nest site selection and nest features. The survey was conducted at margins of two permanent ponds in Southern Brazil. Habitat factors were evaluated in 18 plots with nest and 18 plots in the surrounding without nest (control, describing vegetation structure and heterogeneity, and substrate characteristics. Water temperature was measured inside the nest and in its adjacency. Nest features assessed were area, depth and temperature. Habitat characteristics differed between plots with and without nest. Microhabitat selected for nest-building was characterized by great vegetation cover and height, as well as shallower water and lower cover of organic matter in suspension than in plots without nest. Differences between temperature inside nest and in its adjacency were not observed. No relationship between nest features and habitat descriptors was evidenced. Results revealed that Hypsiboas faber does not build nests anywhere. Males seem to prefer more protected habitats, probably avoiding predation, invasion of conspecific males and inclement weather. Lack of differences between temperature inside- and outside-nest suggest that nest do not improve this

  11. Artificial covering on trap nests improves the colonization of trap-nesting wasps

    OpenAIRE

    Taki, Hisatomo; Kevan, Peter G.; Viana, Blandina Felipe; Silva, Fabiana O.; Buck, Matthias

    2008-01-01

    Acesso restrito: Texto completo. p. 225-229 To evaluate the role that a trap-nest cover might have on sampling methodologies, the abundance of each species of trap-nesting Hymenoptera and the parasitism rate in a Canadian forest were compared between artificially covered and uncovered traps. Of trap tubes exposed at eight forest sites in six trap-nest boxes, 531 trap tubes were occupied and 1216 individuals of 12 wasp species of four predatory families, Vespidae (Eumeninae), Crabronidae...

  12. Nesting ecology and nest survival of lesser prairie-chickens on the Southern High Plains of Texas

    Science.gov (United States)

    Grisham, Blake A.; Borsdorf, Philip K.; Boal, Clint W.; Boydston, Kathy K.

    2014-01-01

    nesting season that provided visual obstruction from predators.

  13. Nested Potential Games

    OpenAIRE

    Hiroshi Uno

    2007-01-01

    This paper proposes a new class of potential games, the nested potential games, which generalize the potential games defined in Monderer and Shapley (1996), as well as the pseudo-potential games defined in Dubey et al. (2006). We show that each maximizer of a nested potential is a Nash equilibrium.

  14. Interspecific interactions in solitary Aculeata - is the presence of heterospecifics important for females establishing nests?

    Science.gov (United States)

    Kierat, J; Miler, K; Celary, W; Woyciechowski, M

    2018-02-01

    There are several possible causes of aggregated nesting in solitary Aculeata, one being joint defense against parasites. We tested whether females prefer nesting in aggregations, even if they consist of heterospecifics. We compared the colonization and nesting parasitism of trap-nests with and without a red mason bee aggregation. The results did not support our hypothesis that females prefer nesting in aggregations. The numbers of wild Aculeata nests did not differ between trap-nests with and without an aggregation. Unexpectedly, parasitism rates were higher in trap-nests with aggregations. When analyzing only nests of wild insects (mostly wasps), the differences in parasitism disappeared. Natural nesting sites may be such a limited resource that females nested in the first trap-nest they encountered and did not discriminate between our treatments, or wasps might share too few parasites species with bees to benefit from joint nest defense.

  15. Research, Monitoring, and Evaluation of Avian Predation on Salmonid Smolts in the Lower and Mid-Columbia River, 2006 Final Season Summary.

    Energy Technology Data Exchange (ETDEWEB)

    Roby, Daniel D. [USGS - Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University; Collis, Ken [Real Time Research, Inc.; Lyons, Donald E. [USGS - Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University

    2009-06-18

    statistically significant change in the size of the Caspian tern colony on East Sand Island since 2000. Tern nesting success averaged 0.72 fledglings per breeding pair in 2006, significantly higher than in 2005 (0.37 fledglings per breeding pair), a year of poor ocean conditions. Despite the presumably higher availability of marine forage fishes in 2006, the proportion of juvenile salmonids in diets of Caspian terns (32% of prey items) averaged higher than in 2005 (23% of prey items) and 2004 (18% of prey items). Steelhead smolts were particular vulnerable to predation by East Sand Island terns in 2006, with predation rates as high as 20% on particular groups of PIT-tagged fish reaching the estuary. Consumption of juvenile salmonids by terns nesting at the East Sand Island colony in 2006 was approximately 5.3 million smolts (95% c.i. = 4.4-6.2 million), significantly higher than the estimated 3.6 million smolts consumed in 2005, but still roughly 7 million fewer smolts consumed compared to 1998 (when all terns nested on Rice Island in the upper estuary). Caspian terns nesting on East Sand Island continue to rely primarily on marine forage fishes as a food supply, even in 2005 when availability of marine forage fishes declined due to poor ocean conditions. Further management of Caspian terns to reduce losses of juvenile salmonids would be implemented under the Caspian Tern Management Plan for the Columbia River Estuary; the Records of Decision (RODs) authorizing implementation of the plan were signed in November 2006. The ROD lists as the management goal the redistribution of approximately half of the East Sand Island Caspian tern colony to alternative colony sites in interior Oregon and San Francisco Bay, California (USFWS 2006). Implementation of the management plan is stalled, however, because of the lack of appropriated funds.

  16. Effects of an infectious fungus, Batrachochytrium dendrobatidis, on amphibian predator-prey interactions.

    Directory of Open Access Journals (Sweden)

    Barbara A Han

    2011-02-01

    Full Text Available The effects of parasites and pathogens on host behaviors may be particularly important in predator-prey contexts, since few animal behaviors are more crucial for ensuring immediate survival than the avoidance of lethal predators in nature. We examined the effects of an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis, on anti-predator behaviors of tadpoles of four frog species. We also investigated whether amphibian predators consumed infected prey, and whether B. dendrobatidis caused differences in predation rates among prey in laboratory feeding trials. We found differences in anti-predator behaviors among larvae of four amphibian species, and show that infected tadpoles of one species (Anaxyrus boreas were more active and sought refuge more frequently when exposed to predator chemical cues. Salamander predators consumed infected and uninfected tadpoles of three other prey species at similar rates in feeding trials, and predation risk among prey was unaffected by B. dendrobatidis. Collectively, our results show that even sub-lethal exposure to B. dendrobatidis can alter fundamental anti-predator behaviors in some amphibian prey species, and suggest the unexplored possibility that indiscriminate predation between infected and uninfected prey (i.e., non-selective predation could increase the prevalence of this widely distributed pathogen in amphibian populations. Because one of the most prominent types of predators in many amphibian systems is salamanders, and because salamanders are susceptible to B. dendrobatidis, our work suggests the importance of considering host susceptibility and behavioral changes that could arise from infection in both predators and prey.

  17. The effects of patch shape and connectivity on nest site selection and reproductive success of the Indigo Bunting.

    Energy Technology Data Exchange (ETDEWEB)

    Weldon, Aimee Jean

    2004-07-01

    Description – Ph.D Dissertation. North Carolina State University. Raleigh, North Carolina. 135 pp. Abatract - Habitat fragmentation and its associated effects have been blamed for the recent population declines of many Neotropical migratory bird species. Increased predation and parasitism resulting from edge-related effects have been implicated for poor nesting success in many studies, mostly of forest interior species. However, little attention has been devoted to disturbance-dependent birds. In this study, I examine how patch shape and connectivity in fragmented landscapes affects the reproductive success of disturbance-dependent bird species, specifically the Indigo Bunting (Passerina cyanea). I conducted my study in a landscape-scale experimental system of similar-area habitat patches that differed in connectivity and in shape. Shapes differed between edgy and rectangular forms, where edgy patches contained 50% more edge than rectangular patches. I tested whether edgy patches function as ecological traps for species with strong edge preferences, by leading them to select dangerous habitats. Indigo Buntings preferentially selected edgy patches over rectangular patches, but experienced significantly lower reproductive success in edgy patches early in the season. Although predation pressure intensified in rectangular patches late in the season, seasonal fecundity was still significantly lower in edgy patches, providing the first empirical evidence that edges can function as ecological traps for Indigo Buntings. A second objective of my study was to evaluate the efficacy of conservation corridors for disturbance-dependent bird species. Conservation corridors have become a popular strategy to preserve biodiversity and promote gene flow in fragmented landscapes, but corridors may also have negative consequences. I tested the hypothesis that corridors can increase nest predation risk in connected patches relative to unconnected patches. Nest predation rates

  18. Nest destruction elicits indiscriminate con- versus heterospecific brood parasitism in a captive bird.

    Science.gov (United States)

    Shaw, Rachael C; Feeney, William E; Hauber, Mark E

    2014-12-01

    Following nest destruction, the laying of physiologically committed eggs (eggs that are ovulated, yolked, and making their way through the oviduct) in the nests of other birds is considered a viable pathway for the evolution of obligate interspecific brood parasitism. While intraspecific brood parasitism in response to nest predation has been experimentally demonstrated, this pathway has yet to be evaluated in an interspecific context. We studied patterns of egg laying following experimental nest destruction in captive zebra finches, Taeniopygia guttata, a frequent intraspecific brood parasite. We found that zebra finches laid physiologically committed eggs indiscriminately between nests containing conspecific eggs and nests containing heterospecific eggs (of Bengalese finches, Lonchura striata vars. domestica), despite the con- and heterospecific eggs differing in both size and coloration. This is the first experimental evidence that nest destruction may provide a pathway for the evolution of interspecific brood parasitism in birds.

  19. Determining sensitive stages for learning to detect predators in ...

    Indian Academy of Sciences (India)

    2014-07-10

    Jul 10, 2014 ... Successful survival and reproduction of prey organisms depend on their ability to detect their potential predators accurately and respond ... Numerous aquatic prey including insects, ... window (pre-gastrulation, neurulation, post-hatching or ..... their increased encounter rates with predators provide them the.

  20. Effect of Slave Raiding of Polyergus samurai on Nest Persistency of Its Host, Formica (Serviformica) japonica

    OpenAIRE

    Hasegawa, Eisuke; Yamaguchi, Takeshi

    1997-01-01

    The effect of slave raiding of Polyergus samurai on nest persistency of its host, Formica (Serviformica) japonica was investigated. Nest persistence rate after the raiding season was not different between raided and unraided nests. Many raided nests stopped aboveground activities for 2-3 weeks after a raiding but surviving workers maintained underground nest structure. These observations suggest that it is required to reconsider the previous interpretation that the raided nests died out from ...

  1. Habitat structure and diversity influence the nesting success of an endangered large cavity-nesting bird, the Southern Ground-hornbill

    OpenAIRE

    Combrink, Leigh; Combrink, Hendrik J.; Botha, André J.; Downs, Colleen T.

    2017-01-01

    Habitat features can have a profound effect on the nesting success of birds. Savannas are often managed with predators and large herbivores as priority species, with little thought to the many bird species that management decisions could affect. Using a data set spanning seven breeding seasons, we examined how nesting success of Southern Ground-hornbills (SGHs) Bucorvus leadbeateri in the Kruger National Park varied as a result of various environmental and habitat factors within a radius of 3...

  2. Healthy Dental Pulp Oxygen Saturation Rates in Subjects with Homozygous Sickle Cell Anemia: A Cross-Sectional Study Nested in a Cohort.

    Science.gov (United States)

    Souza, Soraia de Fátima Carvalho; Thomaz, Erika Bárbara Abreu Fonseca; Costa, Cyrene Piazera Silva

    2017-12-01

    To compare the percentage of arterial oxygen saturation (SpO 2 ) in healthy teeth with confirmed pulp vitality between individuals with sickle cell anemia (HbSS) and normal hemoglobin A (HbAA). This is a cross-sectional study nested within a cohort. Samples (n = 2543) comprised teeth with intact crowns and pulp vitality confirmed by thermal sensitivity tests and no history of caries, periodontal disease, or dental trauma. A total of 728 teeth of 113 individuals with HbSS and 1815 teeth of 246 individuals with HbAA were evaluated. Data analysis was performed using the χ 2 and Mann-Whitney tests and Spearman correlation analysis (α = 0.05). The study groups were comparable in terms of age, race, and sex (P > .05). Subjects with HbSS exhibited lower median SpO 2 levels in the body and upper teeth, excluding canines, than subjects with HbAA (P  .05). Compared with individuals with HbAA, those with HbSS exhibited lower SpO 2 in maxillary teeth with confirmed pulp vitality, except in the canines. There was no correlation between SpO 2 levels of the body and dental pulp in individuals with HbSS or HbAA. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  3. What regulates crab predation on mangrove propagules?

    Science.gov (United States)

    Van Nedervelde, Fleur; Cannicci, Stefano; Koedam, Nico; Bosire, Jared; Dahdouh-Guebas, Farid

    2015-02-01

    Crabs play a major role in some ecosystems. To increase our knowledge about the factors that influence crab predation on propagules in mangrove forests, we performed experiments in Gazi Bay, Kenya in July 2009. We tested whether: (1) crab density influences propagule predation rate; (2) crab size influences food competition and predation rate; (3) crabs depredate at different rates according to propagule and canopy cover species; (4) vegetation density is correlated with crab density; (5) food preferences of herbivorous crabs are determined by size, shape and nutritional value. We found that (1) propagule predation rate was positively correlated to crab density. (2) Crab competitive abilities were unrelated to their size. (3) Avicennia marina propagules were consumed more quickly than Ceriops tagal except under C. tagal canopies. (4) Crab density was negatively correlated with the density of A. marina trees and pneumatophores. (5) Crabs prefer small items with a lower C:N ratio. Vegetation density influences crab density, and crab density affects propagule availability and hence vegetation recruitment rate. Consequently, the mutual relationships between vegetation and crab populations could be important for forest restoration success and management.

  4. Testing mechanistic explanations for mammalian predator responses to habitat edges

    Czech Academy of Sciences Publication Activity Database

    Svobodová, J.; Kreisinger, J.; Šálek, Martin; Koubová, M.; Albrecht, Tomáš

    2011-01-01

    Roč. 57, č. 3 (2011), s. 467-474 ISSN 1612-4642 R&D Projects: GA MŠk 1P05OC078; GA ČR GA524/06/0687; GA MŠk LC06073 Institutional research plan: CEZ:AV0Z60930519; CEZ:AV0Z60870520 Keywords : Edge effect * Habitat fragmentation * Mesopredators * Nest predation * Prey distribution Subject RIV: EH - Ecology, Behaviour Impact factor: 1.306, year: 2011

  5. Local and landscape drivers of predation services in urban gardens.

    Science.gov (United States)

    Philpott, Stacy M; Bichier, Peter

    2017-04-01

    In agroecosystems, local and landscape features, as well as natural enemy abundance and richness, are significant predictors of predation services that may result in biological control of pests. Despite the increasing importance of urban gardening for provisioning of food to urban populations, most urban gardeners suffer from high pest problems, and have little knowledge about how to manage their plots to increase biological control services. We examined the influence of local, garden scale (i.e., herbaceous and arboreal vegetation abundance and diversity, ground cover) and landscape (i.e., landscape diversity and surrounding land use types) characteristics on predation services provided by naturally occurring predators in 19 urban gardens in the California central coast. We introduced sentinel pests (moth eggs and larvae and pea aphids) onto greenhouse-raised plants taken to gardens and assigned to open or bagged (predator exclosure) treatments. We found high predation rates with between 40% and 90% of prey items removed in open treatments. Predation services varied with local and landscape factors, but significant predictors differed by prey species. Predation of eggs and aphids increased with vegetation complexity in gardens, but larvae predation declined with vegetation complexity. Smaller gardens experienced higher predation services, likely due to increases in predator abundance in smaller gardens. Several ground cover features influenced predation services. In contrast to patterns in rural agricultural landscapes, predation on aphids declined with increases in landscape diversity. In sum, we report the relationships between several local management factors, as well as landscape surroundings, and implications for garden management. © 2017 by the Ecological Society of America.

  6. Predator Exclosures Enhance Reproductive Success but Increase Adult Mortality of Piping Plovers (Charadrius melodus

    Directory of Open Access Journals (Sweden)

    Colleen Barber

    2010-12-01

    Full Text Available Piping Plovers (Charadrius melodus are listed as endangered throughout Canada and the United States Great Lakes region. Most attempts to increase their numbers have focused on enhancing reproductive success. Using 22 years of data collected by Parks Canada in Prince Edward Island National Park of Canada, we examined whether predator exclosures installed around Piping Plover nests increased nest success and hatching and fledging success when compared to nests without exclosures. Nests with exclosures were significantly more likely to hatch at least one egg than nests without exclosures, and they hatched a significantly greater number of young. The greater reproductive success observed in exclosed nests is likely due to the increased protection from predators that the exclosures conferred; significantly fewer exclosed nests were depredated than nonexclosed nests. However, significantly more exclosed than nonexclosed nests were abandoned by adults, and they had significantly greater adult mortality. Whether benefits of increased reproductive success from exclosures outweigh costs of increased abandonment and adult mortality remains unknown, but must be considered.

  7. Flown The Nest

    OpenAIRE

    Sebbane, Nathalie

    2012-01-01

    Lorsque le quotidien régional, The Champion, commence à publier Flown The Nest en 1972 sous forme d’épisodes, Bird’s Nest Soup est déjà en vente, et la troisième partie de l’autobiographie d’Hanna, Housekeeper At Large, est sous presse. L’édition de 2009 contient Flown The Nest et Housekeeper at Large. Dans Bird’s Nest Soup, Hanna Greally racontait les dix-huit années de sa vie passées au sein d’un hôpital psychiatrique. Les raisons pour lesquelles elle y avait été enfermée, à la demande de s...

  8. Hydrological disturbance diminishes predator control in wetlands.

    Science.gov (United States)

    Dorn, Nathan J; Cook, Mark I

    2015-11-01

    Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades.

  9. Camouflage predicts survival in ground-nesting birds.

    Science.gov (United States)

    Troscianko, Jolyon; Wilson-Aggarwal, Jared; Stevens, Martin; Spottiswoode, Claire N

    2016-01-29

    Evading detection by predators is crucial for survival. Camouflage is therefore a widespread adaptation, but despite substantial research effort our understanding of different camouflage strategies has relied predominantly on artificial systems and on experiments disregarding how camouflage is perceived by predators. Here we show for the first time in a natural system, that survival probability of wild animals is directly related to their level of camouflage as perceived by the visual systems of their main predators. Ground-nesting plovers and coursers flee as threats approach, and their clutches were more likely to survive when their egg contrast matched their surrounds. In nightjars - which remain motionless as threats approach - clutch survival depended on plumage pattern matching between the incubating bird and its surrounds. Our findings highlight the importance of pattern and luminance based camouflage properties, and the effectiveness of modern techniques in capturing the adaptive properties of visual phenotypes.

  10. Optimal diving under the risk of predation.

    Science.gov (United States)

    Heithaus, Michael R; Frid, Alejandro

    2003-07-07

    Many air-breathing aquatic foragers may be killed by aerial or subsurface predators while recovering oxygen at the surface; yet the influence of predation risk on time allocation during dive cycles is little known in spite of numerous studies on optimal diving. We modeled diving behavior under the risk of predation at the surface. The relationship between time spent at the surface and the risk of death is predicted to influence the optimal surface interval, regardless of whether foragers accumulate energy at a constant rate while at the food patch, deplete food resources over the course of the dive, or must search for food during the dive. When instantaneous predation risk during a single surface interval decreases with time spent at the surface, a diver should increase its surface interval relative to that which maximizes energy intake, thereby increasing dive durations and reducing the number of surfacings per foraging bout. When instantaneous risk over a single surface interval does not change or increases with increasing time at the surface, divers should decrease their surface interval (and consequently their dive duration) relative to that which maximizes energy intake resulting in more dives per foraging bout. The fitness consequences of selecting a suboptimal surface interval vary with the risk function and the way divers harvest energy when at depth. Finally, predation risk during surface intervals should have important consequences for habitat selection and other aspects of the behavioral ecology of air-breathing aquatic organisms.

  11. Effectiveness of nest site restoration for the endangered northern map turtle. Report no. 1 : nest site selection and nest success from 2013-2014 and establishment of environmental center.

    Science.gov (United States)

    2015-05-01

    The Northern Map Turtle, Graptemys geographica, is a Maryland state Endangered Species, found only in the : lower Susquehanna River in Maryland. The only area where nests of this species are not heavily impacted by : predators occurs in the town of P...

  12. Concentrated nesting of mallards and gadwalls on Miller Lake Island, North Dakota

    Science.gov (United States)

    Duebbert, H.F.; Lokemoen, J.T.; Sharp, D.E.

    1983-01-01

    Island-nesting mallards (Anas platyrhynchos) and gadwalls (A. strepera) were studied on a 4.5-ha island in 385-ha Miller Lake in northwestern North Dakota during 1976-80. During the 5-year study, 2,561 duck nests of 9 species were found on Island A located 180 m offshore; 59% were mallard and 34% were gadwall. In patches of shrub cover, which contained the greatest concentrations of nests, densities ranged from 241 to 389 mallard nests/ha and from 139 to 237 gadwall nests/ha. Over 97% of the nests were placed in 4 patches of shrubs totaling about 1 ha of western snowberry (Symphoricarpos occidentalis)--Woods rose (Rosa woodsii) cover, which composed about 30% of the island's vegetation. Average hatching success was 85% for clutches of all species. Abandonment averaged 14% (348 of 2,426 nests) and was the major cause of egg failure. Only 15 nests (eggs in successful nests averaged 83% for mallards and 87% for gadwalls. Despite the close spacing of nests, most individual hens maintained normal nesting regimes. Eighty-one percent of the mallard clutches contained 7-13 eggs and 81% of the gadwall clutches contained 8-14 eggs. Island A in Miller Lake provides an outstanding example of the potential for high reproduction levels of mallards and gadwalls nesting in small areas of predator-free habitats.

  13. Seasonal shift in the effects of predators on juvenile Atlantic salmon (Salmo salar) energetics

    Science.gov (United States)

    Darren M. Ward; Keith H. Nislow; Carol L. Folt; James Grant

    2011-01-01

    Predator effects on prey populations are determined by the number of prey consumed and effects on the traits of surviving prey. Yet the effects of predators on prey traits are rarely evaluated in field studies. We measured the effects of predators on energetic traits (consumption and growth rates) of juvenile Atlantic salmon (Salmo salar) in a...

  14. Nest Site Characteristics of Cavity Nesting Birds in Central Missouri

    Science.gov (United States)

    Jeffery D. Brawn; Bernice Tannenbaum; Keith E. Evans

    1984-01-01

    Two study sites in central Missouri oak-hickory forests were searched for nest sites of cavity nesting birds. Researchers located and measured 133 nests of 11 species. Cavity nesting bird habitat selection is affected by both snag characteristics and vegetation structure.

  15. Predator control promotes invasive dominated ecological states.

    Science.gov (United States)

    Wallach, Arian D; Johnson, Christopher N; Ritchie, Euan G; O'Neill, Adam J

    2010-08-01

    Invasive species are regarded as one of the top five drivers of the global extinction crisis. In response, extreme measures have been applied in an attempt to control or eradicate invasives, with little success overall. We tested the idea that state shifts to invasive dominance are symptomatic of losses in ecosystem resilience, due to the suppression of apex predators. This concept was investigated in Australia where the high rate of mammalian extinctions is largely attributed to the destructive influence of invasive species. Intensive pest control is widely applied across the continent, simultaneously eliminating Australia's apex predator, the dingo (Canis lupus dingo). We show that predator management accounts for shifts between two main ecosystem states. Lethal control fractures dingo social structure and leads to bottom-up driven increases in invasive mesopredators and herbivores. Where control is relaxed, dingoes re-establish top-down regulation of ecosystems, allowing for the recovery of biodiversity and productivity.

  16. The influence of regional hydrology on nesting behavior and nest fate of the American alligator

    Science.gov (United States)

    Ugarte, Cristina A.; Bass, Oron L.; Nuttle, William; Mazzotti, Frank J.; Rice, Kenneth G.; Fujisaki, Ikuko; Whelan, Kevin R.T.

    2013-01-01

    Hydrologic conditions are critical to the nesting behavior and reproductive success of crocodilians. In South Florida, USA, growing human settlement has led to extensive surface water management and modification of historical water flows in the wetlands, which have affected regional nesting of the American alligator (Alligator mississippiensis). Although both natural and anthropogenic factors are considered to determine hydrologic conditions, the aspects of hydrological patterns that affect alligator nest effort, flooding (partial and complete), and failure (no hatchling) are unclear. We deconstructed annual hydrological patterns using harmonic models that estimated hydrological matrices including mean, amplitude, timing of peak, and periodicity of surface water depth and discharge and examined their effects on alligator nesting using survey data from Shark Slough, Everglades National Park, from 1985 to 2005. Nest effort increased in years with higher mean and lesser periodicity of water depth. A greater proportion of nests were flooded and failed when peak discharge occurred earlier in the year. Also, nest flooding rates were greater in years with greater periodicity of water depth, and nest failure rate was greater when mean discharge was higher. This study guides future water management decisions to mitigate negative impacts on reproduction of alligators and provides wildlife managers with a tool for assessing and modifying annual water management plans to conserve crocodilians and other wetland species.

  17. Predation of Five Generalist Predators on Brown Planthopper (Nilaparvata lugens Stål

    Directory of Open Access Journals (Sweden)

    Sri Karindah

    2015-09-01

    Full Text Available Two generalist predators of brown planthopper,Metioche vittaticollis and Anaxipha longipennis (Gryllidae have not been much studied in Indonesia. This research was conducted to study and compare the predatory ability of M. vittaticollis, A. longipennis (Gryllidae and three coleopterans, Paederus fuscipes (Staphylinidae, Ophionea sp. (Carabidae,and Micraspis sp. (Coccinellidae against brown planthopper (fourth and fifth instars under laboratory condition. In total, 20 nymphs of N. lugens were exposed for 2 hour to each predator for 5 consecutive days. Prey consumptions by the predatory crickets, M. vittaticollis and A. longipennis were greater than the other predators and followed by A. longipennis, Micraspis sp., P. fuscipes, and Ophionea sp. respectively. Consumption rates of M. vittaticolis and A. longipenis were also higher than other predators. Micraspis sp was more active on predation in the morning,while M. vittaticollis, A. longipennis, P. fuscipes, and Ophionea sp. were more active both in the morning and the night but not in the afternoon. However, all five species of predators were not so active in preying during the afternoon. In conclusion, a major effort should be extended to conserve these predatory crickets especially M. vittaticollis and A. longipennis.

  18. Predators control post-fledging mortality in tawny owls, Strix aluco

    DEFF Research Database (Denmark)

    Sunde, Peter

    2005-01-01

    , primarily due to predation from raptors and mammals (predominantly foxes Vulpes vulpes). Predation by mammals occurred within the first few days after fledging, with young leaving the nest at an early age being at particularly high risk. Young that had received extra food as nestlings were also at higher...... risk of being preyed upon by mammals, possibly because they were easier to locate on their smell. Total mortality risk (control broods) increased with fledging date from 14% in April to >58% in June due to an increasing raptor predation risk. Individual attributes such as sex, condition......, immunocompetence or prevalence of blood parasites did not predict total or cause-specific mortality risk. Survival during the post-fledging dependency period was therefore primarily a function of variation in predation pressures, particularly from raptors. Increasing raptor predation of late broods appears...

  19. Nested and Hierarchical Archimax copulas

    KAUST Repository

    Hofert, Marius; Huser, Raphaë l; Prasad, Avinash

    2017-01-01

    The class of Archimax copulas is generalized to nested and hierarchical Archimax copulas in several ways. First, nested extreme-value copulas or nested stable tail dependence functions are introduced to construct nested Archimax copulas based on a single frailty variable. Second, a hierarchical construction of d-norm generators is presented to construct hierarchical stable tail dependence functions and thus hierarchical extreme-value copulas. Moreover, one can, by itself or additionally, introduce nested frailties to extend Archimax copulas to nested Archimax copulas in a similar way as nested Archimedean copulas extend Archimedean copulas. Further results include a general formula for the density of Archimax copulas.

  20. Nested and Hierarchical Archimax copulas

    KAUST Repository

    Hofert, Marius

    2017-07-03

    The class of Archimax copulas is generalized to nested and hierarchical Archimax copulas in several ways. First, nested extreme-value copulas or nested stable tail dependence functions are introduced to construct nested Archimax copulas based on a single frailty variable. Second, a hierarchical construction of d-norm generators is presented to construct hierarchical stable tail dependence functions and thus hierarchical extreme-value copulas. Moreover, one can, by itself or additionally, introduce nested frailties to extend Archimax copulas to nested Archimax copulas in a similar way as nested Archimedean copulas extend Archimedean copulas. Further results include a general formula for the density of Archimax copulas.

  1. A community-level evaluation of the impact of prey behavioural and ecological characteristics on predator diet composition.

    Science.gov (United States)

    Shultz, Susanne; Noë, Ronald; McGraw, W Scott; Dunbar, R I M

    2004-04-07

    Although predation avoidance is the most commonly invoked explanation for vertebrate social evolution, there is little evidence that individuals in larger groups experience lower predation rates than those in small groups. We compare the morphological and behavioural traits of mammal prey species in the Taï forest, Ivory Coast, with the diet preferences of three of their non-human predators: leopards, chimpanzees and African crowned eagles. Individual predators show marked differences in their predation rates on prey species of different body sizes, but clear patterns with prey behaviour were apparent only when differences in prey habitat use were incorporated into the analyses. Leopard predation rates are highest for terrestrial species living in smaller groups, whereas eagle predation rates are negatively correlated with group size only among arboreal prey. When prey predation rates are summed over all three predators, terrestrial species incur higher predation rates than arboreal species and, within both categories, predation rates decline with increasing prey group size and decreasing density of groups in the habitat. These results reveal that it is necessary to consider anti-predator strategies in the context of a dynamic behavioural interaction between predators and prey.

  2. The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata

    OpenAIRE

    Elahi, Robin

    2005-01-01

    The large predatory ant, Paraponera clavata, exerts measurable top-down effects in wet and moist Neotropical forests, and therefore its distribution has potential ecological implications. To determine how water affects the presence of this important predator, the ground nesting ecology of P. clavata was examined with respect to various habitat characteristics. Four hectares of disturbed Costa Rican lowland rain forest were surveyed for ant colonies to determine nest distribution patterns in w...

  3. Insect Seed Predators in Erythrina falcata (Fabaceae): Identification of Predatory Species and Ecological Consequences of Asynchronous Flowering.

    Science.gov (United States)

    Pereira, C M; Moura, M O; Da-Silva, P R

    2014-06-01

    Seed predation by insects exerts negative effects on plant reproduction by limiting the supply of seeds and preventing germination. Seed predators of the family Fabaceae are usually generalists, which increases the rate of predation. One strategy to minimize seed predation, developed by plants from temperate regions, is "escape in time," i.e., flowering before or after the peak of predation. For tropical species, few studies have investigated the strategies used by plants to minimize seed predation. Here, using Erythrina falcata, a tropical species of Fabaceae, we test three main hypotheses: (i) escape in time is a mechanism used by E. falcata to minimize seed predation, (ii) the predators of E. falcata seeds are generalists, and (iii) the biometric variables of the pods can influence seed predation. In order to test these hypotheses, we determined the flowering time of E. falcata, rate of seed predation, the predators insects, and biometric variables of the pods. The analyzed trees were grouped into three classes: "early," "peak," and "late" flowering. The average seed predation rates on trees in the early and late classes were 65% and 50%, respectively, and in the peak class, 80%; thus, our first hypothesis can be accepted. Three species of Lepidoptera and two of Coleoptera were found preying on E. falcata seeds. These species were observed to be generalist predators; thus, our second hypothesis can be accepted. The biometric variables of the pods cannot influence seed predation rate. The ecological consequences of asynchronous flowering on plants and insects are discussed.

  4. Patch size and edge proximity are useful predictors of brood parasitism but not nest survival of grassland birds.

    Science.gov (United States)

    Benson, Thomas J; Chiavacci, Scott J; Ward, Michael P

    2013-06-01

    Declines of migratory birds have led to increased focus on causative factors for these declines, including the potential adverse effects of habitat fragmentation on reproductive success. Although numerous studies have addressed how proximity to a habitat edge, patch size, or landscape context influence nest survival or brood parasitism, many have failed to find the purported effects. Furthermore, many have sought to generalize patterns across large geographic areas and habitats. Here, we examined evidence for effects of edge proximity, patch size, and landscape context on nest survival and brood parasitism of grassland birds, a group of conservation concern. The only consistent effect was a positive association between edge proximity and brood parasitism. We examined effects of patch size on nest survival (37 studies) and brood parasitism (30 studies) representing 170 and 97 different estimates, respectively, with a total sample size of > 14000 nests spanning eastern North America. Nest survival weakly increased with patch size in the Great Plains, but not in the Midwestern or Eastern United States, and brood parasitism was inversely related to patch size and consistently greater in the Great Plains. The consistency in brood parasitism relative to nest survival patterns is likely due to parasitism being caused by one species, while nest survival is driven by a diverse and variable suite of nest predators. Often, studies assume that predators responsible for nest predation, the main driver of nest success, either are the same or exhibit the same behaviors across large geographic areas. These results suggest that a better mechanistic understanding of nest predation is needed to provide meaningful conservation recommendations for improving grassland bird productivity, and that the use of general recommendations across large geographic areas should only be undertaken when sufficient data are available from all regions.

  5. Breeding biology and nest site characteristics of the Rosy-faced ...

    African Journals Online (AJOL)

    Nine colonies, comprising 20 nests, were monitored every four days to establish incubation and fledging periods. Rearing and fledging of chicks was found to be successful in eight nests. Measurements of 18 young from four nests were used to monitor growth rate. Nesting success was calculated at 0.1, following the ...

  6. Superposition Enhanced Nested Sampling

    Directory of Open Access Journals (Sweden)

    Stefano Martiniani

    2014-08-01

    Full Text Available The theoretical analysis of many problems in physics, astronomy, and applied mathematics requires an efficient numerical exploration of multimodal parameter spaces that exhibit broken ergodicity. Monte Carlo methods are widely used to deal with these classes of problems, but such simulations suffer from a ubiquitous sampling problem: The probability of sampling a particular state is proportional to its entropic weight. Devising an algorithm capable of sampling efficiently the full phase space is a long-standing problem. Here, we report a new hybrid method for the exploration of multimodal parameter spaces exhibiting broken ergodicity. Superposition enhanced nested sampling combines the strengths of global optimization with the unbiased or athermal sampling of nested sampling, greatly enhancing its efficiency with no additional parameters. We report extensive tests of this new approach for atomic clusters that are known to have energy landscapes for which conventional sampling schemes suffer from broken ergodicity. We also introduce a novel parallelization algorithm for nested sampling.

  7. Serenbe Nest Cottages

    Energy Technology Data Exchange (ETDEWEB)

    Butler, T.; Curtis, O.; Kim, E.; Roberts, S.; Stephenson, R.

    2012-12-01

    As part of the NAHB Research Center Industry Partnership, Southface partnered with Martin Dodson Builders and the Serenbe community on the construction of a new test home in the suburbs of Atlanta, GA in the mixed humid climate zone. The most recent subdivision within the Serenbe community, the Nest, will contain 15 small footprint cottage style homes, and Southface has selected Lot Nine, as the test home for this study. This Nest subdivision serves as a project showcase for both the builder partner and the Serenbe community as a whole. The planning and design incorporated into the Nest cottages will be implemented in each home within the subdivision. These homes addresses Building America Savings targets and serve as a basis of design for other homes Martin Dodson plans to build within the Serenbe community.

  8. Serenbe Nest Cottages

    Energy Technology Data Exchange (ETDEWEB)

    Butler, T. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States); Curtis, O. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States); Kim, E. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States); Roberts, S. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States); Stephenson, R. [NAHB Research Center Industry Partnership, Upper Marlboro, MD (United States)

    2012-12-01

    As part of the NAHB Research Center Industry Partnership, Southface partnered with Martin Dodson Builders and the Serenbe community on the construction of a new test home in the suburbs of Atlanta, GA, in the mixed humid climate zone. The most recent subdivision within the Serenbe community, the Nest, will contain 15 small footprint cottage-style homes, and Southface has selected Lot Nine, as the test home for this study. This Nest subdivision serves as a project showcase for both the builder partner and the Serenbe community as a whole. The planning and design incorporated into the Nest cottages will be implemented in each home within the subdivision. These homes addresses Building America savings targets and serve as a basis of design for other homes Martin Dodson plans to build within the Serenbe community.

  9. Mink predation on brown trout in a Black Hills stream

    Science.gov (United States)

    Davis, Jacob L.; Wilhite, Jerry W.; Chipps, Steven R.

    2016-01-01

    In the early 2000’s, declines in the brown trout (Salmo trutta) fishery in Rapid Creek, South Dakota, caused concern for anglers and fisheries managers. We conducted a radio telemetry study in 2010 and 2011 to identify predation mortality associated with mink, using hatchery-reared (2010) or wild (2011) brown trout. Estimated predation rates by mink (Mustela vison) on radio-tagged brown trout were 30% for hatchery fish and 32% for wild fish. Size frequency analysis revealed that the size distribution of brown trout lost to predation was similar to that of other, radio-tagged brown trout. In both years, a higher proportion of predation mortality (83–92%) occurred during spring, consistent with seasonal fish consumption by mink. Predation by mink appeared to be a significant source of brown trout mortality in our study.

  10. Habitat structure and diversity influence the nesting success of an endangered large cavity-nesting bird, the Southern Ground-hornbill

    Directory of Open Access Journals (Sweden)

    Leigh Combrink

    2017-11-01

    Full Text Available Habitat features can have a profound effect on the nesting success of birds. Savannas are often managed with predators and large herbivores as priority species, with little thought to the many bird species that management decisions could affect. Using a data set spanning seven breeding seasons, we examined how nesting success of Southern Ground-hornbills (SGHs Bucorvus leadbeateri in the Kruger National Park varied as a result of various environmental and habitat factors within a radius of 3 km surrounding the nest site. Identifying which factors affect nesting success will allow for targeted management efforts to ensure the long-term survival of SGHs both within and outside of protected areas. Habitat structure and diversity of the vegetation surrounding the nest were the most influential factors on SGH nesting success. SGHs require open grassy areas for foraging and areas with large trees for nesting. Savanna habitat drivers such as elephants and fire should be managed to ensure that sufficient large trees are able to establish in the landscape and to control for bush encroachment. This is especially important in areas earmarked for SGH reintroductions. Nest sites of SGHs should be monitored to mitigate any structural changes in the habitat surrounding the nests. Nests should be modified or artificial nest sites provided, where nests have been damaged or lost, to ensure the continued presence of these birds in African savannas. Conservation implications: Habitat structure and diversity surrounding Southern Groundhornbill nests has a significant impact on their nesting success. This highlights the importance of monitoring vegetation change in savanna habitats where they occur. Management of savanna areas should take factors that influence bush encroachment, such as fire and elephants, into account to ensure the long-term persistence of these birds.

  11. Plastic responses of a sessile prey to multiple predators: a field and experimental study.

    Directory of Open Access Journals (Sweden)

    Philipp Emanuel Hirsch

    Full Text Available Theory predicts that prey facing a combination of predators with different feeding modes have two options: to express a response against the feeding mode of the most dangerous predator, or to express an intermediate response. Intermediate phenotypes protect equally well against several feeding modes, rather than providing specific protection against a single predator. Anti-predator traits that protect against a common feeding mode displayed by all predators should be expressed regardless of predator combination, as there is no need for trade-offs.We studied phenotypic anti-predator responses of zebra mussels to predation threat from a handling-time-limited (crayfish and a gape-size-limited (roach predator. Both predators dislodge mussels from the substrate but diverge in their further feeding modes. Mussels increased expression of a non-specific defense trait (attachment strength against all combinations of predators relative to a control. In response to roach alone, mussels showed a tendency to develop a weaker and more elongated shell. In response to crayfish, mussels developed a harder and rounder shell. When exposed to either a combination of predators or no predator, mussels developed an intermediate phenotype. Mussel growth rate was positively correlated with an elongated weaker shell and negatively correlated with a round strong shell, indicating a trade-off between anti-predator responses. Field observations of prey phenotypes revealed the presence of both anti-predator phenotypes and the trade-off with growth, but intra-specific population density and bottom substrate had a greater influence than predator density.Our results show that two different predators can exert both functionally equivalent and inverse selection pressures on a single prey. Our field study suggests that abiotic factors and prey population density should be considered when attempting to explain phenotypic diversity in the wild.

  12. How do Neoseiulus californicus (Acari: Phytoseiidae) females penetrate densely webbed spider mite nests?

    Science.gov (United States)

    Montserrat, M; de la Peña, F; Hormaza, J I; González-Fernández, J J

    2008-02-01

    The persea mite Oligonychus perseae is a pest of avocado trees that builds extremely dense webbed nests that protect them against natural enemies, including phytoseiid mites. Nests have one or two marginal entrances that are small and flattened. The predatory mite Neoseiulus californicus co-occurs with O. perseae in the avocado orchards of the south-east of Spain. Penetration inside nests through the entrances by this predator is thought to be hindered by its size and its globular-shaped body. However, in the field it has repeatedly been found inside nests that were clearly ripped. Perhaps penetration of the nests has been facilitated by nest wall ripping caused by some other species or by unfavourable abiotic factors. However, to assess whether N. californicus is also able to enter the nest of O. perseae by itself, we carried out laboratory experiments and made a short film. They show how this predator manages to overcome the webbed wall, and that it can penetrate and forage inside nests of O. perseae.

  13. Presence of Breeding Birds Improves Body Condition for a Crocodilian Nest Protector.

    Science.gov (United States)

    Nell, Lucas A; Frederick, Peter C; Mazzotti, Frank J; Vliet, Kent A; Brandt, Laura A

    2016-01-01

    Ecological associations where one species enhances habitat for another nearby species (facilitations) shape fundamental community dynamics and can promote niche expansion, thereby influencing how and where species persist and coexist. For the many breeding birds facing high nest-predation pressure, enemy-free space can be gained by nesting near more formidable animals for physical protection. While the benefits to protected species seem well documented, very few studies have explored whether and how protector species are affected by nest protection associations. Long-legged wading birds (Pelecaniformes and Ciconiiformes) actively choose nesting sites above resident American alligators (Alligator mississippiensis), apparently to take advantage of the protection from mammalian nest predators that alligator presence offers. Previous research has shown that wading bird nesting colonies could provide substantial food for alligators in the form of dropped chicks. We compared alligator body condition in similar habitat with and without wading bird nesting colonies present. Alligator morphometric body condition indices were significantly higher in colony than in non-colony locations, an effect that was statistically independent of a range of environmental variables. Since colonially nesting birds and crocodilians co-occur in many tropical and subtropical wetlands, our results highlight a potentially widespread keystone process between two ecologically important species-groups. These findings suggest the interaction is highly beneficial for both groups of actors, and illustrate how selective pressures may have acted to form and reinforce a strongly positive ecological interaction.

  14. Presence of Breeding Birds Improves Body Condition for a Crocodilian Nest Protector

    Science.gov (United States)

    Nell, Lucas A.; Frederick, Peter C.; Mazzotti, Frank J.; Vliet, Kent A.; Brandt, Laura A.

    2016-01-01

    Ecological associations where one species enhances habitat for another nearby species (facilitations) shape fundamental community dynamics and can promote niche expansion, thereby influencing how and where species persist and coexist. For the many breeding birds facing high nest-predation pressure, enemy-free space can be gained by nesting near more formidable animals for physical protection. While the benefits to protected species seem well documented, very few studies have explored whether and how protector species are affected by nest protection associations. Long-legged wading birds (Pelecaniformes and Ciconiiformes) actively choose nesting sites above resident American alligators (Alligator mississippiensis), apparently to take advantage of the protection from mammalian nest predators that alligator presence offers. Previous research has shown that wading bird nesting colonies could provide substantial food for alligators in the form of dropped chicks. We compared alligator body condition in similar habitat with and without wading bird nesting colonies present. Alligator morphometric body condition indices were significantly higher in colony than in non-colony locations, an effect that was statistically independent of a range of environmental variables. Since colonially nesting birds and crocodilians co-occur in many tropical and subtropical wetlands, our results highlight a potentially widespread keystone process between two ecologically important species-groups. These findings suggest the interaction is highly beneficial for both groups of actors, and illustrate how selective pressures may have acted to form and reinforce a strongly positive ecological interaction. PMID:26934602

  15. Nest survival is influenced by parental behaviour and heterospecifics in a mixed-species colony

    Science.gov (United States)

    Brussee, Brianne E.; Coates, Peter S.; Hothem, Roger L.; Howe, Kristy; Casazza, Michael L.; Eadie, John M.

    2016-01-01

    Studies of avian nest success often focus on examining influences of variation in environmental and seasonal factors. However, in-depth evaluations can also incorporate variation in individual incubation behaviour to further advance our understanding of avian reproductive ecology. We examined these relationships in colonially nesting Black-crowned Night-Herons Nycticorax nycticorax using intensive video-monitoring methods to quantify incubation behaviours. We modelled nest survival as a function of both extrinsic factors and incubation behaviours over a 3-year period (2010–12) on Alcatraz Island, USA. Model-averaged parameter estimates indicated that nest survival increased as a function of greater incubation constancy (% of time spent incubating eggs within a 24-h period), and average daily precipitation throughout the nesting stage. Common Ravens Corvus corax are the only known nest predator of Night-Herons on Alcatraz Island, as on many other coastal Pacific islands. We also investigated the effects of heterospecific nesting of California Gulls Larus californicus and Western Gulls Larus occidentalis in a mixed-species colony with Night-Herons, based on nesting proximity data collected over a 2-year period (2011–12). This second analysis indicated that, in addition to incubation behaviours, nesting heterospecifics are an important factor for explaining variation in Night-Heron nest survival. However, contrary to our original expectation, we found that Night-Herons experienced increased nest survival with increasing distance from gull colony boundaries. These results may apply to other areas with multiple colonial nesting species and similar predator communities and climatic patterns.

  16. Prey aggregation is an effective olfactory predator avoidance strategy

    Directory of Open Access Journals (Sweden)

    Asa Johannesen

    2014-05-01

    Full Text Available Predator–prey interactions have a major effect on species abundance and diversity, and aggregation is a well-known anti-predator behaviour. For immobile prey, the effectiveness of aggregation depends on two conditions: (a the inability of the predator to consume all prey in a group and (b detection of a single large group not being proportionally easier than that of several small groups. How prey aggregation influences predation rates when visual cues are restricted, such as in turbid water, has not been thoroughly investigated. We carried out foraging (predation experiments using a fish predator and (dead chironomid larvae as prey in both laboratory and field settings. In the laboratory, a reduction in visual cue availability (in turbid water led to a delay in the location of aggregated prey compared to when visual cues were available. Aggregated prey suffered high mortality once discovered, leading to better survival of dispersed prey in the longer term. We attribute this to the inability of the dead prey to take evasive action. In the field (where prey were placed in feeding stations that allowed transmission of olfactory but not visual cues, aggregated (large groups and semi-dispersed prey survived for longer than dispersed prey—including long term survival. Together, our results indicate that similar to systems where predators hunt using vision, aggregation is an effective anti-predator behaviour for prey avoiding olfactory predators.

  17. Canada goose nest survival at rural wetlands in north-central Iowa

    Science.gov (United States)

    Ness, Brenna N.; Klaver, Robert W.

    2016-01-01

    The last comprehensive nest survival study of the breeding giant Canada goose (Branta canadensis maxima) population in Iowa, USA, was conducted >30 years ago during a period of population recovery, during which available nesting habitat consisted primarily of artificial nest structures. Currently, Iowa's resident goose population is stable and nests in a variety of habitats. We analyzed the effects of available habitat on nest survival and how nest survival rates compared with those of the expanding goose population studied previously to better understand how to maintain a sustainable Canada goose population in Iowa. We documented Canada goose nest survival at rural wetland sites in north-central Iowa. We monitored 121 nests in 2013 and 149 nests in 2014 at 5 Wildlife Management Areas (WMAs) with various nesting habitats, including islands, muskrat (Ondatra zibethicus) houses, and elevated nest structures. We estimated daily nest-survival rate using the nest survival model in Program MARK. Survival was influenced by year, site, stage, presence of a camera, nest age, and an interaction between nest age and stage. Nest success rates for the 28-day incubation period by site and year combination ranged from 0.10 to 0.84. Nest survival was greatest at sites with nest structures (β = 17.34). Nest survival was negatively affected by lowered water levels at Rice Lake WMA (2013 β = −0.77, nest age β = −0.07). Timing of water-level drawdowns for shallow lake restorations may influence nest survival rates.

  18. Predator avoidance in extremophile fish.

    Science.gov (United States)

    Bierbach, David; Schulte, Matthias; Herrmann, Nina; Zimmer, Claudia; Arias-Rodriguez, Lenin; Indy, Jeane Rimber; Riesch, Rüdiger; Plath, Martin

    2013-02-06

    Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis.

  19. Predator Avoidance in Extremophile Fish

    Science.gov (United States)

    Bierbach, David; Schulte, Matthias; Herrmann, Nina; Zimmer, Claudia; Arias-Rodriguez, Lenin; Indy, Jeane Rimber; Riesch, Rüdiger; Plath, Martin

    2013-01-01

    Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis. PMID:25371337

  20. Inhibition between invasives: a newly introduced predator moderates the impacts of a previously established invasive predator.

    Science.gov (United States)

    Griffen, Blaine D; Guy, Travis; Buck, Julia C

    2008-01-01

    1. With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. Interactions between invasive species may provide important mechanisms that moderate their impacts on native species. 2. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid-1800 s and is capable of rapid consumption of bivalve prey. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus, was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions as C. maenas within the Gulf of Maine. Using a series of field and laboratory investigations, we examined the consequences of interactions between these predators. 3. Density patterns of these two species at different spatial scales are consistent with negative interactions. As a result of these interactions, C. maenas alters its diet to consume fewer mussels, its preferred prey, in the presence of H. sanguineus. Decreased mussel consumption in turn leads to lower growth rates for C. maenas, with potential detrimental effects on C. maenas populations. 4. Rather than an invasional meltdown, this study demonstrates that, within the Gulf of Maine, this new invasive predator can moderate the impacts of the older invasive predator.

  1. The importance of illumination in nest site choice and nest characteristics of cavity nesting birds.

    Science.gov (United States)

    Podkowa, Paweł; Surmacki, Adrian

    2017-05-02

    Light has a significant impact on many aspects of avian biology, physiology and behaviour. An increasing number of studies show that illumination may positively influences birds' offspring fitness by e.g. acceleration of embryo development, stimulation of skeleton growth or regulation of circadian rhythm. Because nest cavities have especially low illumination, suitable light levels may be especially important for species which nest there. We may therefore expect that birds breeding in relatively dim conditions should prefer brighter nest sites and/or evolve behavioral mechanisms to secure sufficient light levels in the nest. Using nest boxes with modified internal illumination, we experimentally tested whether light regime is a cue for nest site selection of secondary cavity-nesting species. Additionally, we investigated whether nest building strategies are tuned to internal illumination. Our results demonstrate that, nest boxes with elevated illumination were chosen twice as often as dark nest boxes. Moreover, birds built higher nests in dark nest boxes than birds in boxes with elevated illumination, which suggests a mechanism of compensating for low light conditions. Our results provide the first experimental support for the idea that nest site choice and nest building behaviour in cavity-nesting birds are influenced by ambient illumination.

  2. Contrasting Effects of Cattle Grazing Intensity on Upland-Nesting Duck Production at Nest and Field Scales in the Aspen Parkland, Canada

    Directory of Open Access Journals (Sweden)

    Jeffrey M. Warren

    2008-12-01

    field was 33.9% (95% CI = 17.0-51.8%. Across the range of residual cover observed in this study, nests with above-average nest-site vegetation density had nesting success rates that exceeded the levels believed necessary to maintain duck populations. Our findings on complex and previously unreported relationships between grazing, nest density, and nesting success provide useful insights into the management and conservation of ground-nesting grassland birds.

  3. Top predators induce the evolutionary diversification of intermediate predator species.

    Science.gov (United States)

    Zu, Jian; Yuan, Bo; Du, Jianqiang

    2015-12-21

    We analyze the evolutionary branching phenomenon of intermediate predator species in a tritrophic food chain model by using adaptive dynamics theory. Specifically, we consider the adaptive diversification of an intermediate predator species that feeds on a prey species and is fed upon by a top predator species. We assume that the intermediate predator׳s ability to forage on the prey can adaptively improve, but this comes at the cost of decreased defense ability against the top predator. First, we identify the general properties of trade-off relationships that lead to a continuously stable strategy or to evolutionary branching in the intermediate predator species. We find that if there is an accelerating cost near the singular strategy, then that strategy is continuously stable. In contrast, if there is a mildly decelerating cost near the singular strategy, then that strategy may be an evolutionary branching point. Second, we find that after branching has occurred, depending on the specific shape and strength of the trade-off relationship, the intermediate predator species may reach an evolutionarily stable dimorphism or one of the two resultant predator lineages goes extinct. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  4. The cavity-nest ant Temnothorax crassispinus prefers larger nests.

    Science.gov (United States)

    Mitrus, S

    Colonies of the ant Temnothorax crassispinus inhabit mostly cavities in wood and hollow acorns. Typically in the field, nest sites that can be used by the ant are a limited resource. In a field experiment, it was investigated whether the ants prefer a specific size of nest, when different ones are available. In July 2011, a total of 160 artificial nests were placed in a beech-pine forest. Four artificial nests (pieces of wood with volume cavities, ca 415, 605, 730, and 980 mm 3 , respectively) were located on each square meter of the experimental plot. One year later, shortly before the emergence of new sexuals, the nests were collected. In July 2012, colonies inhabited more frequently bigger nests. Among queenright colonies, the ones which inhabited bigger nests had more workers. However, there was no relationship between volume of nest and number of workers for queenless colonies. Queenright colonies from bigger nests produced more sexual individuals, but there was no correlation between number of workers and sex allocation ratio, or between volume of nest and sex allocation ratio. In a laboratory experiment where ant colonies were kept in 470 and 860 mm 3 nests, larger colonies allocated more energy to produce sexual individuals. The results of this study show the selectivity of T. crassispinus ants regarding the size of nest cavity, and that the nest volume has an impact on life history parameters.

  5. Feathering Your Nest

    Science.gov (United States)

    Nabors, Martha L.; Edwards, Linda Carol; Decker, Suzanne

    2010-01-01

    The first-grade classroom was like a natural history museum. Bird nests of every shape and size lay on top of bookshelves that lined two walls. Methods students, who were visiting the classroom in preparation for the science lessons they would teach there, were immediately inspired by the collection. They used the collection as a springboard for…

  6. Fiber Tracking Cylinder Nesting

    International Nuclear Information System (INIS)

    Stredde, H.

    1999-01-01

    The fiber tracker consists of 8 concentric carbon fiber cylinders of varying diameters, from 399mm to 1032.2mm and two different lengths. 1.66 and 2.52 meters. Each completed cylinder is covered over the entire o.d. with scintillating fiber ribbons with a connector on each ribbon. These ribbons are axial (parallel to the beam line) at one end and stereo (at 3 deg. to the beam line) at the other. The ribbon connectors have dowel pins which are used to match with the connectors on the wave guide ribbons. These dowel pins are also used during the nesting operation, locating and positioning measurements. The nesting operation is the insertion of one cylinder into another, aligning them with one another and fastening them together into a homogeneous assembly. For ease of assembly. the nesting operation is accomplished working from largest diameter to smallest. Although the completed assembly of all 8 cylinders glued and bolted together is very stiff. individual cylinders are relatively flexible. Therefore. during this operation, No.8 must be supported in a manner which maintains its integrity and yet allows the insertion of No.7. This is accomplished by essentially building a set of dummy end plates which replicate a No.9 cylinder. These end plates are mounted on a wheeled cart that becomes the nesting cart. Provisions for a protective cover fastened to these rings has been made and will be incorporated in finished product. These covers can be easily removed for access to No.8 and/or the connection of No.8 to No.9. Another wheeled cart, transfer cart, is used to push a completed cylinder into the cylinder(s) already mounted in the nesting cart.

  7. Prey life-history and bioenergetic responses across a predation gradient.

    Science.gov (United States)

    Rennie, M D; Purchase, C F; Shuter, B J; Collins, N C; Abrams, P A; Morgan, G E

    2010-10-01

    To evaluate the importance of non-consumptive effects of predators on prey life histories under natural conditions, an index of predator abundance was developed for naturally occurring populations of a common prey fish, the yellow perch Perca flavescens, and compared to life-history variables and rates of prey energy acquisition and allocation as estimated from mass balance models. The predation index was positively related to maximum size and size at maturity in both male and female P. flavescens, but not with life span or reproductive investment. The predation index was positively related to size-adjusted specific growth rates and growth efficiencies but negatively related to model estimates of size-adjusted specific consumption and activity rates in both vulnerable (small) and invulnerable (large) size classes of P. flavescens. These observations suggest a trade-off between growth and activity rates, mediated by reduced activity in response to increasing predator densities. Lower growth rates and growth efficiencies in populations with fewer predators, despite increased consumption suggests either 1) a reduction in prey resources at lower predator densities or 2) an intrinsic cost of rapid prey growth that makes it unfavourable unless offset by a perceived threat of predation. This study provides evidence of trade-offs between growth and activity rates induced by predation risk in natural prey fish populations and illustrates how behavioural modification induced through predation can shape the life histories of prey fish species. © 2010 The Authors. Journal compilation © 2010 The Fisheries Society of the British Isles.

  8. Understanding predation: implications toward forest management

    Science.gov (United States)

    Harvey R. Smith

    1991-01-01

    It is generally accepted that when gypsy moths rest in the litter survival is low due to predation by ground-foraging generalist predators and that predation can maintain these populations indefinitely. Forest Service research on predators of gypsy moth continues to focus on population dynamics, the mechanisms of predation and forest management implications.

  9. Effect of Egg Size on Predation by White-Footed Mice

    Science.gov (United States)

    R. M. DeGraaf; T. J. Maier

    1996-01-01

    We compared predation by wild-trapped, caged white-footed mice (Peromyscus leucopus) on eggs of Japanese Quail (Coturnix coturnix) and Zebra Finches (Poephila guttata) to test the effect of egg size. Nine male and nine female mice were weighed, acclimated to cages for 24 h, and presented with two wicker nests,...

  10. Tufted puffins (Fratercula cirrhata) respond to predation danger during colony approach flights

    NARCIS (Netherlands)

    Addison, B.; Ydenberg, R.C.; Smith, B.D.

    2007-01-01

    In spite of their putative importance in the evolution of certain traits (e.g., nocturnality, coloniality, cliff nesting), the effects of aerial predators on behavior of adult seabirds at colonies have been poorly investigated. We hypothesized that Tufted Puffins (Fratercula cirrhata) respond to

  11. Predator response to releases of American shad larvae in the Susquehanna River basin

    Science.gov (United States)

    Johnson, James H.; Ringler, N.H.

    1998-01-01

    Predation on American shad (Alosa sapidissima) larvae within the first two hours of release was examined from 1989 to 1992 on 31 occasions at stocking sites in the Susquehanna River basin. Twenty-two fish species consumed shad larvae; the dominant predators were spotfin shiner (Cyprinella spiloptera), mimic shiner (Notropis volucellus) and juvenile smallmouth bass (Micropterus dolomieu). The number of shad larvae found in predator stomachs ranged from 0 to 900. Mortality of shad larvae at the stocking site was usually less than 2%. The greatest mortality (9.6%) occurred at the highest stocking level (1.5 million larvae). Highly variable predation rates and release levels of shad insufficient to achieve predator satiation hindered the ability to determine a specific type of functional response of predators. Predator numbers increased with stocking density, indicating short-term aggregation at the release site. Because of practical problems associated with releasing the large numbers of larvae that would be required to satiate predators, routine stocking at these levels is probably unreasonable. Releases of 400,000 to 700,000 larvae may reduce predation by offsetting depensatory mechanisms that operate on small releases and the effects of increased predation due to predator aggregation on large releases. Night stocking may reduce predation on larval shad at the release site.

  12. Nest-site selection and nest success of an Arctic-breeding passerine, Smith's Longspur, in a changing climate

    Science.gov (United States)

    McFarland, Heather R.; Kendall, Steve J.; Powell, Abby

    2017-01-01

    Despite changes in shrub cover and weather patterns associated with climate change in the Arctic, little is known about the breeding requirements of most passerines tied to northern regions. We investigated the nesting biology and nest habitat characteristics of Smith's Longspurs (Calcarius pictus) in 2 study areas in the Brooks Range of Alaska, USA. First, we examined variation in nesting phenology in relation to local temperatures. We then characterized nesting habitat and analyzed nest-site selection for a subset of nests (n = 86) in comparison with paired random points. Finally, we estimated the daily survival rate of 257 nests found in 2007–2013 with respect to both habitat characteristics and weather variables. Nest initiation was delayed in years with snow events, heavy rain, and freezing temperatures early in the breeding season. Nests were typically found in open, low-shrub tundra, and never among tall shrubs (mean shrub height at nests = 26.8 ± 6.7 cm). We observed weak nest-site selection patterns. Considering the similarity between nest sites and paired random points, coupled with the unique social mating system of Smith's Longspurs, we suggest that habitat selection may occur at the neighborhood scale and not at the nest-site scale. The best approximating model explaining nest survival suggested a positive relationship with the numbers of days above 21°C that an individual nest experienced; there was little support for models containing habitat variables. The daily nest survival rate was high (0.972–0.982) compared with that of most passerines in forested or grassland habitats, but similar to that of passerines nesting on tundra. Considering their high nesting success and ability to delay nest initiation during inclement weather, Smith's Longspurs may be resilient to predicted changes in weather regimes on the breeding grounds. Thus, the greatest threat to breeding Smith's Longspurs associated with climate change may be the loss of low

  13. Bat Predation by Spiders

    Science.gov (United States)

    Nyffeler, Martin; Knörnschild, Mirjam

    2013-01-01

    In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (∼90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S). Most reports refer to the Neotropics (42% of observed incidences), Asia (28.8%), and Australia-Papua New Guinea (13.5%). Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter). The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64%) and Emballonuridae (22%) and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death), there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation). This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed. PMID:23516436

  14. Bat predation by spiders.

    Science.gov (United States)

    Nyffeler, Martin; Knörnschild, Mirjam

    2013-01-01

    In this paper more than 50 incidences of bats being captured by spiders are reviewed. Bat-catching spiders have been reported from virtually every continent with the exception of Antarctica (≈ 90% of the incidences occurring in the warmer areas of the globe between latitude 30° N and 30° S). Most reports refer to the Neotropics (42% of observed incidences), Asia (28.8%), and Australia-Papua New Guinea (13.5%). Bat-catching spiders belong to the mygalomorph family Theraphosidae and the araneomorph families Nephilidae, Araneidae, and Sparassidae. In addition to this, an attack attempt by a large araneomorph hunting spider of the family Pisauridae on an immature bat was witnessed. Eighty-eight percent of the reported incidences of bat catches were attributable to web-building spiders and 12% to hunting spiders. Large tropical orb-weavers of the genera Nephila and Eriophora in particular have been observed catching bats in their huge, strong orb-webs (of up to 1.5 m diameter). The majority of identifiable captured bats were small aerial insectivorous bats, belonging to the families Vespertilionidae (64%) and Emballonuridae (22%) and usually being among the most common bat species in their respective geographic area. While in some instances bats entangled in spider webs may have died of exhaustion, starvation, dehydration, and/or hyperthermia (i.e., non-predation death), there were numerous other instances where spiders were seen actively attacking, killing, and eating the captured bats (i.e., predation). This evidence suggests that spider predation on flying vertebrates is more widespread than previously assumed.

  15. Ground-nesting marine birds and potential for human disturbance in Glacier Bay National Park

    Science.gov (United States)

    Arimitsu, Mayumi L.; Romano, Marc D.; Piatt, John F.; Piatt, John F.; Gende, S.M.

    2004-01-01

    Glacier Bay National Park and Preserve contains a diverse assemblage of marine birds that use the area for nesting, foraging and molting. The abundance and diversity of marine bird species in Glacier Bay is unmatched in the region, due in part to the geomorphic and successional characteristics that result in a wide array of habitat types (Robards and others, 2003). The opportunity for proactive management of these species is unique in Glacier Bay National Park because much of the suitable marine bird nesting habitat occurs in areas designated as wilderness. Ground-nesting marine birds are vulnerable to human disturbance wherever visitors can access nest sites during the breeding season. Human disturbance of nest sites can be significant because intense parental care is required for egg and hatchling survival, and repeated disturbance can result in reduced productivity (Leseberg and others, 2000). Temporary nest desertion by breeding birds in disturbed areas can lead to increased predation on eggs and hatchlings by conspecifics or other predators (Bolduc and Guillemette, 2003). Human disturbance of ground-nesting birds may also affect incubation time and adult foraging success, which in turn can alter breeding success (Verhulst and others, 2001). Furthermore, human activity can potentially cause colony failure when disturbance prevents the initiation of nesting (Hatch, 2002). There is management concern about the susceptibility of breeding birds to disturbance from human activities, but little historical data has been collected on the distribution of ground-nesting marine birds in Glacier Bay. This report summarizes results obtained during two years of a three-year study to determine the distribution of ground-nesting marine birds in Glacier Bay, and the potential for human disturbance of those nesting birds.

  16. Nest protection in mallards Anas platyrhynchos: untangling the role of crypsis and parental behaviour

    Czech Academy of Sciences Publication Activity Database

    Kreisinger, J.; Albrecht, Tomáš

    2008-01-01

    Roč. 22, č. 5 (2008), s. 872-879 ISSN 0269-8463 R&D Projects: GA MŠk LC06073 Institutional research plan: CEZ:AV0Z60930519 Keywords : anti-predation behaviour * nest construction * parental compensation hypothesis * waterfowl Subject RIV: EG - Zoology Impact factor: 3.699, year: 2008

  17. Determinants of stingless bee nest density in lowland dipterocarp forests of Sabah, Malaysia.

    Science.gov (United States)

    Eltz, Thomas; Brühl, Carsten A; van der Kaars, Sander; Linsenmair, Eduard K

    2002-03-01

    We measured the nest density of stingless bees (Apidae, Meliponini) in undisturbed and logged-over dipterocarp forests in Sabah, northern Borneo, and evaluated hypotheses on proximate factors leading to the observed variation: population control mediated by (1) nest predation, (2) limitation of nest trees, or (3) food limitation. Per-area nest density varied twentyfold across 14 forest sites and was significantly affected by locality, but not by the degree and history of disturbance. Nest density was generally high in sites located in the Sepilok Forest fragment (mean 8.4 nests/ha), bordering mangroves or plantations. In contrast, nest densities in continuous forests were all low (between 0 and 2.1 nests/ha, mean 0.5 nests/ha). Yearly nest mortality was low (13.5-15.0%) over 4 years of observation and did not vary between forest localities, thus limiting the potential of nest predation (1) in creating the observed variation in nest density. The presence of potential nest trees (2), though positively correlated with nest density, explained only a minute fraction of the observed variation. Nest density was best explained by differences in the pollen resources (3) available to the bees (quantified by analysis of pollen in bee garbage). Across five selected sites the amount of nonforest pollen (from mangrove or crop plants) included in diets of Trigona collina was positively correlated with T. collina nest density. External pollen sources are a likely supplement to bee diets at times when little flowering occurs inside the forest, thus increasing overall bee carrying capacity. Pollen limitation was also indicated by direct measurements of pollen import and foraging activity of T. collina in three selected sites: Pollen traps installed at nests in high-density Sepilok captured significantly more corbicular pollen than colonies in low-density Deramakot. At the same time, morning foraging activity was also greater in Sepilok, indicating a regulatory increase in foraging

  18. Use of no-till winter wheat by nesting ducks in North Dakota

    Science.gov (United States)

    Duebbert, H.F.; Kantrud, H.A.

    1987-01-01

    Nesting of dabbling ducks (Anatinae) was studied in fields of no-till winter wheat (Triticum aestivum) in the prairie pothole region of North Dakota during 1984 and 1985. Total area of 59 fields searched in 1984 was 1,135 ha and total area of 70 fields searched in 1985 was 1,175 ha. Field sizes ranged from 3 ha to 110 ha. Nests of five duck species were found: blue-winged teal (Anas discors), 55 nests; northern pintail (A. acuta), 44; mallard (A. platyrhynchos), 29; gadwall (A. strepera), 15; and northern shoveler (A. clypeata), 8. The average number of nests found was 8/100 ha in 1984 and 6/100 ha in 1985. Nest success for all species averaged 26% in 1984 and 29% in 1985. Predation by mammals was the principal cause of nest destruction. No egg or hen mortality could be attributed to pesticide use. Only 6 of 151 nests (4%) were abandoned during the two years. We also found 29 nests of seven other ground-nesting bird species. The trend toward increased planting of no-till winter wheat in the prairie pothole region should benefit production of ducks and other ground-nesting birds.

  19. Fortune favours the bold: a higher predator reduces the impact of a native but not an invasive intermediate predator.

    Science.gov (United States)

    Barrios-O'Neill, Daniel; Dick, Jaimie T A; Emmerson, Mark C; Ricciardi, Anthony; MacIsaac, Hugh J; Alexander, Mhairi E; Bovy, Helene C

    2014-05-01

    Emergent multiple predator effects (MPEs) might radically alter predictions of predatory impact that are based solely on the impact of individuals. In the context of biological invasions, determining if and how the individual-level impacts of invasive predators relates to their impacts in multiple-individual situations will inform understanding of how such impacts might propagate through recipient communities. Here, we use functional responses (the relationship between prey consumption rate and prey density) to compare the impacts of the invasive freshwater mysid crustacean Hemimysis anomala with a native counterpart Mysis salemaai when feeding on basal cladoceran prey (i) as individuals, (ii) in conspecific groups and (iii) in conspecific groups in the presence of a higher fish predator, Gasterosteus aculeatus. In the absence of the higher predator, the invader consumed significantly more basal prey than the native, and consumption was additive for both mysid species - that is, group consumption was predictable from individual-level consumption. Invaders and natives were themselves equally susceptible to predation when feeding with the higher fish predator, but an MPE occurred only between the natives and higher predator, where consumption of basal prey was significantly reduced. In contrast, consumption by the invaders and higher predator remained additive. The presence of a higher predator serves to exacerbate the existing difference in individual-level consumption between invasive and native mysids. We attribute the mechanism responsible for the MPE associated with the native to a trait-mediated indirect interaction, and further suggest that the relative indifference to predator threat on the part of the invader contributes to its success and impacts within invaded communities. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

  20. Nested cellular automata

    International Nuclear Information System (INIS)

    Quasthoff, U.

    1985-07-01

    Cellular automata by definition consist of a finite or infinite number of cells, say of unit length, with each cell having the same transition function. These cells are usually considered as the smallest elements and so the space filled with these cells becomes discrete. Nevertheless, large pictures created by such cellular automata look very fractal. So we try to replace each cell by a couple of smaller cells, which have the same transition functions as the large ones. There are automata where this replacement does not destroy the macroscopic structure. In these cases this nesting process can be iterated. The paper contains large classes of automata with the above properties. In the case of one dimensional automata with two states and next neighbour interaction and a nesting function of the same type a complete classification is given. (author)

  1. Adrenocortical responses to offspring-directed threats in two open-nesting birds.

    Science.gov (United States)

    Butler, Luke K; Bisson, Isabelle-Anne; Hayden, Timothy J; Wikelski, Martin; Romero, L Michael

    2009-07-01

    Dependent young are often easy targets for predators, so for many parent vertebrates, responding to offspring-directed threats is a fundamental part of reproduction. We tested the parental adrenocortical response of the endangered black-capped vireo (Vireo atricapilla) and the common white-eyed vireo (V. griseus) to acute and chronic threats to their offspring. Like many open-nesting birds, our study species experience high offspring mortality. Parents responded behaviorally to a predator decoy or human 1-2m from their nests, but, in contrast to similar studies of cavity-nesting birds, neither these acute threats nor chronic offspring-directed threats altered plasma corticosterone concentrations of parents. Although parents in this study showed no corticosterone response to offspring-directed threats, they always increased corticosterone concentrations in response to capture. To explain these results, we propose that parents perceive their risk of nest-associated death differently depending on nest type, with cavity-nesting adults perceiving greater risk to themselves than open-nesters that can readily detect and escape from offspring-directed threats. Our results agree with previous studies suggesting that the hypothalamic-pituitary-adrenal axis, a major physiological mechanism for coping with threats to survival, probably plays no role in coping with threats to offspring when risks to parents and offspring are not correlated. We extend that paradigm by demonstrating that nest style may influence how adults perceive the correlation between offspring-directed and self-directed threats.

  2. A meta-analysis of predation risk effects on pollinator behaviour.

    Directory of Open Access Journals (Sweden)

    Gustavo Q Romero

    Full Text Available Flower-visiting animals are constantly under predation risk when foraging and hence might be expected to evolve behavioural adaptations to avoid predators. We reviewed the available published and unpublished data to assess the overall effects of predators on pollinator behaviour and to examine sources of variation in these effects. The results of our meta-analysis showed that predation risk significantly decreased flower visitation rates (by 36% and time spent on flowers (by 51% by pollinators. The strength of the predator effects depended neither on predator taxa and foraging mode (sit-and-wait or active hunters nor on pollinator lifestyle (social vs. solitary. However, predator effects differed among pollinator taxa: predator presence reduced flower visitation rates and time spent on flowers by Squamata, Lepidoptera and Hymenoptera, but not by Diptera. Furthermore, larger pollinators showed weaker responses to predation risk, probably because they are more difficult to capture. Presence of live crab spiders on flowers had weaker effects on pollinator behaviour than presence of dead or artificial crab spiders or other objects (e.g. dead bees, spheres, suggesting that predator crypsis may be effective to some extent. These results add to a growing consensus on the importance of considering both predator and pollinator characteristics from a community perspective.

  3. A meta-analysis of predation risk effects on pollinator behaviour.

    Science.gov (United States)

    Romero, Gustavo Q; Antiqueira, Pablo A P; Koricheva, Julia

    2011-01-01

    Flower-visiting animals are constantly under predation risk when foraging and hence might be expected to evolve behavioural adaptations to avoid predators. We reviewed the available published and unpublished data to assess the overall effects of predators on pollinator behaviour and to examine sources of variation in these effects. The results of our meta-analysis showed that predation risk significantly decreased flower visitation rates (by 36%) and time spent on flowers (by 51%) by pollinators. The strength of the predator effects depended neither on predator taxa and foraging mode (sit-and-wait or active hunters) nor on pollinator lifestyle (social vs. solitary). However, predator effects differed among pollinator taxa: predator presence reduced flower visitation rates and time spent on flowers by Squamata, Lepidoptera and Hymenoptera, but not by Diptera. Furthermore, larger pollinators showed weaker responses to predation risk, probably because they are more difficult to capture. Presence of live crab spiders on flowers had weaker effects on pollinator behaviour than presence of dead or artificial crab spiders or other objects (e.g. dead bees, spheres), suggesting that predator crypsis may be effective to some extent. These results add to a growing consensus on the importance of considering both predator and pollinator characteristics from a community perspective.

  4. Cormorant predation on PIT-tagged lake fish

    DEFF Research Database (Denmark)

    Skov, Christian; Jepsen, Niels; Baktoft, Henrik

    2014-01-01

    The present study use data from recovered PIT (Passive Integrated Transponder) tags to explore species-and size-specific annual predation rates by cormorants on three common lacustrine fishes (size range 120-367 mm) in a European lake; roach (Rutilus rutilus), common bream (Abramis brama) and perch...... (Perca fluviatilis). In addition, we quantify the level of age/size truncation that cormorant predation could introduce in a population of perch, an important fish for recreational angling as well as for trophic interactions and ecosystem function in European lakes. Based on three years of PIT tagging...... of fish in Lake Viborg and subsequent recoveries of PIT tags from nearby cormorant roosting and breeding sites, we show that cormorants are major predators of roach, bream and perch within the size groups we investigated and for all species larger individuals had higher predation rates. Perch appear...

  5. Why wasp foundresses change nests: relatedness, dominance, and nest quality.

    Directory of Open Access Journals (Sweden)

    Perttu Seppä

    Full Text Available The costs and benefits of different social options are best understood when individuals can be followed as they make different choices, something that can be difficult in social insects. In this detailed study, we follow overwintered females of the social wasp Polistes carolina through different nesting strategies in a stratified habitat where nest site quality varies with proximity to a foraging area, and genetic relatedness among females is known. Females may initiate nests, join nests temporarily or permanently, or abandon nests. Females can become helpers or egglayers, effectively workers or queens. What they actually do can be predicted by a combination of ecological and relatedness factors. Advantages through increased lifetime success of individuals and nests drives foundresses of the social wasp Polistes from solitary to social nest founding. We studied reproductive options of spring foundresses of P. carolina by monitoring individually-marked wasps and assessing reproductive success of each foundress by using DNA microsatellites. We examined what behavioral decisions foundresses make after relaxing a strong ecological constraint, shortage of nesting sites. We also look at the reproductive consequences of different behaviors. As in other Polistes, the most successful strategy for a foundress was to initiate a nest as early as possible and then accept others as subordinates. A common feature for many P. carolina foundresses was, however, that they reassessed their reproductive options by actively monitoring other nests at the field site and sometimes moving permanently to new nests should that offer better (inclusive fitness prospects compared to their original nests. A clear motivation for moving to new nests was high genetic relatedness; by the end of the foundress period all females were on nests with full sisters.

  6. Why Wasp Foundresses Change Nests: Relatedness, Dominance, and Nest Quality

    Science.gov (United States)

    Seppä, Perttu; Queller, David C.; Strassmann, Joan E.

    2012-01-01

    The costs and benefits of different social options are best understood when individuals can be followed as they make different choices, something that can be difficult in social insects. In this detailed study, we follow overwintered females of the social wasp Polistes carolina through different nesting strategies in a stratified habitat where nest site quality varies with proximity to a foraging area, and genetic relatedness among females is known. Females may initiate nests, join nests temporarily or permanently, or abandon nests. Females can become helpers or egglayers, effectively workers or queens. What they actually do can be predicted by a combination of ecological and relatedness factors. Advantages through increased lifetime success of individuals and nests drives foundresses of the social wasp Polistes from solitary to social nest founding. We studied reproductive options of spring foundresses of P. carolina by monitoring individually-marked wasps and assessing reproductive success of each foundress by using DNA microsatellites. We examined what behavioral decisions foundresses make after relaxing a strong ecological constraint, shortage of nesting sites. We also look at the reproductive consequences of different behaviors. As in other Polistes, the most successful strategy for a foundress was to initiate a nest as early as possible and then accept others as subordinates. A common feature for many P. carolina foundresses was, however, that they reassessed their reproductive options by actively monitoring other nests at the field site and sometimes moving permanently to new nests should that offer better (inclusive) fitness prospects compared to their original nests. A clear motivation for moving to new nests was high genetic relatedness; by the end of the foundress period all females were on nests with full sisters. PMID:23049791

  7. Skate Bathyraja spp. egg predation in the eastern Bering Sea.

    Science.gov (United States)

    Hoff, G R

    2009-01-01

    Predation on skate eggs by snails was examined for three skate species at seven nursery sites in three regions (north, middle and south) of the eastern Bering Sea. Mean predation levels were 6.46% for the Alaska skate Bathyraja parmifera, 2.65% for the Aleutian skate Bathyraja aleutica and 22.25% for the Bering skate Bathyraja interrupta. Predation levels were significantly higher at the middle and north sites than the south sites for all species combined. Predation levels decreased with increasing egg-case densities at all nursery sites, and the highest predation levels occurred where egg-case densities were very low. Predated egg-case density increased with increasing snail densities across all nursery sites examined. The Oregon triton Fusitriton oregonensis was the most abundant snail species at all nursery sites and displayed ability to drill holes in the egg case of B. parmifera. Holes left by predatory snails in egg cases of B. parmifera were significantly larger, and of different shape at the middle site compared to the south site. Holes in B. parmifera were also significantly larger than those in egg cases of B. interrupta across all sites examined. Egg cases of B. aleutica possess surface spines that cover the egg case and may inhibit predation by snails at a greater rate than that of the B. parmifera and B. interrupta, which have a smoother egg-case surface.

  8. CO2 efflux from subterranean nests of ant communities in a seasonal tropical forest, Thailand.

    Science.gov (United States)

    Hasin, Sasitorn; Ohashi, Mizue; Yamada, Akinori; Hashimoto, Yoshiaki; Tasen, Wattanachai; Kume, Tomonori; Yamane, Seiki

    2014-10-01

    Many ant species construct subterranean nests. The presence of their nests may explain soil respiration "hot spots", an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determined the effects of environmental factors on nest CO2 efflux and calculated an index of nest structure. The mean CO2 efflux from nests was significantly higher than those from the surrounding soil in the wet and dry seasons. The CO2 efflux was species-specific, showing significant differences among the 13 ant species. The soil moisture content significantly affected nest CO2 efflux, but there was no clear relationship between nest CO2 efflux and nest soil temperature. The diameter of the nest entrance hole affected CO2 efflux. However, there was no significant difference in CO2 efflux rates between single-hole and multiple-hole nests. Our results suggest that in a tropical forest ecosystem the increase in CO2 efflux from subterranean ant nests is caused by species-specific activity of ants, the nest soil environment, and nest structure.

  9. Identifying effective actions to guide volunteer-based and nationwide conservation efforts for a ground-nesting farmland bird.

    Science.gov (United States)

    Santangeli, Andrea; Arroyo, Beatriz; Millon, Alexandre; Bretagnolle, Vincent

    2015-08-01

    1. Modern farming practices threaten wildlife in different ways, and failure to identify the complexity of multiple threats acting in synergy may result in ineffective management. To protect ground-nesting birds in farmland, monitoring and mitigating impacts of mechanical harvesting is crucial. 2. Here, we use 6 years of data from a nationwide volunteer-based monitoring scheme of the Montagu's harrier, a ground-nesting raptor, in French farmlands. We assess the effectiveness of alternative nest protection measures and map their potential benefit to the species. 3. We show that unprotected nests in cultivated land are strongly negatively affected by harvesting and thus require active management. Further, we show that protection from harvesting alone (e.g. by leaving a small unharvested buffer around the nest) is impaired by post-harvest predation at nests that become highly conspicuous after harvest. Measures that simultaneously protect from harvesting and predation (by adding a fence around the nest) significantly enhance nest productivity. 4. The map of expected gain from nest protection in relation to available volunteers' workforce pinpoints large areas of high expected gain from nest protection that are not matched by equally high workforce availability. This mismatch suggests that the impact of nest protection can be further improved by increasing volunteer efforts in key areas where they are low relative to the expected gain they could have. 5. Synthesis and applications . This study shows that synergistic interplay of multiple factors (e.g. mechanical harvesting and predation) may completely undermine the success of well-intentioned conservation efforts. However, identifying areas where the greatest expected gains can be achieved relative to effort expended can minimize the risk of wasted volunteer actions. Overall, this study underscores the importance of citizen science for collecting large-scale data useful for producing science and ultimately informs

  10. Lifespan analyses of forest raptor nests: patterns of creation, persistence and reuse.

    Directory of Open Access Journals (Sweden)

    María V Jiménez-Franco

    Full Text Available Structural elements for breeding such as nests are key resources for the conservation of bird populations. This is especially true when structural elements require a specific and restricted habitat, or if the construction of nests is costly in time and energy. The availability of nesting-platforms is influenced by nest creation and persistence. In a Mediterranean forest in southeastern Spain, nesting-platforms are the only structural element for three forest-dwelling raptor species: booted eagle Aquila pennata, common buzzard Buteo buteo and northern goshawk Accipiter gentilis. From 1998 to 2013, we tracked the fate of 157 nesting-platforms built and reused by these species with the aim of determining the rates of creation and destruction of nesting-platforms, estimating nest persistence by applying two survival analyses, describing the pattern of nest reuse and testing the effects of nest use on breeding success. Nest creation and destruction rates were low (0.14 and 0.05, respectively. Using Kaplan Meier survival estimates and Cox proportional-hazards regression models we found that median nest longevity was 12 years and that this was not significantly affected by nest characteristics, nest-tree dimensions, nest-builder species, or frequency of use of the platform. We also estimated a transition matrix, considering the different stages of nest occupation (vacant or occupied by one of the focal species, to obtain the fundamental matrix and the average life expectancies of nests, which varied from 17.9 to 19.7 years. Eighty six percent of nests were used in at least one breeding attempt, 67.5% were reused and 17.8% were successively occupied by at least two of the study species. The frequency of nest use had no significant effects on the breeding success of any species. We conclude that nesting-platforms constitute an important resource for forest raptors and that their longevity is sufficiently high to allow their reuse in multiple breeding

  11. Lifespan Analyses of Forest Raptor Nests: Patterns of Creation, Persistence and Reuse

    Science.gov (United States)

    Jiménez-Franco, María V.; Martínez, José E.; Calvo, José F.

    2014-01-01

    Structural elements for breeding such as nests are key resources for the conservation of bird populations. This is especially true when structural elements require a specific and restricted habitat, or if the construction of nests is costly in time and energy. The availability of nesting-platforms is influenced by nest creation and persistence. In a Mediterranean forest in southeastern Spain, nesting-platforms are the only structural element for three forest-dwelling raptor species: booted eagle Aquila pennata, common buzzard Buteo buteo and northern goshawk Accipiter gentilis. From 1998 to 2013, we tracked the fate of 157 nesting-platforms built and reused by these species with the aim of determining the rates of creation and destruction of nesting-platforms, estimating nest persistence by applying two survival analyses, describing the pattern of nest reuse and testing the effects of nest use on breeding success. Nest creation and destruction rates were low (0.14 and 0.05, respectively). Using Kaplan Meier survival estimates and Cox proportional-hazards regression models we found that median nest longevity was 12 years and that this was not significantly affected by nest characteristics, nest-tree dimensions, nest-builder species, or frequency of use of the platform. We also estimated a transition matrix, considering the different stages of nest occupation (vacant or occupied by one of the focal species), to obtain the fundamental matrix and the average life expectancies of nests, which varied from 17.9 to 19.7 years. Eighty six percent of nests were used in at least one breeding attempt, 67.5% were reused and 17.8% were successively occupied by at least two of the study species. The frequency of nest use had no significant effects on the breeding success of any species. We conclude that nesting-platforms constitute an important resource for forest raptors and that their longevity is sufficiently high to allow their reuse in multiple breeding attempts. PMID

  12. Nesting biology of the trap-nesting Neotropical wasp Trypoxylo n(Trypargilum) aurifrons Shuckard (Hymenoptera, Crabronidae)

    OpenAIRE

    Santoni,Mariana Marchi; Del Lama,Marco Antonio

    2007-01-01

    The present study was carried out in three localities of the state of São Paulo, Brazil: Araras (Dec/03-Dec/06), São Carlos (Nov/04-Nov/06) and Rifaina (Jul/04-Dec/06). Trap-nests were distributed among sites in the sampling areas and were collected every 35 days. Data from 295 nests indicate that T. aurifrons is a multivoltine species, with higher rates of nest building and cell production in the warm, rainy season. The trap-nests used by the females ranged from 117 to 467 mm in length and 3...

  13. Nesting biology of Black-shouldered Kite (Elanus caeruleus in oil palm landscape in Carey Island, Peninsular Malaysia

    Directory of Open Access Journals (Sweden)

    Rosli Ramli

    2018-03-01

    Full Text Available Black-shouldered Kite (Elanus caeruleus is a well-known raptor that inhabits open areas such as oil palm plantation or paddy field. To determine preferable habitat and nesting site of Black-shouldered Kite in oil palm landscape, we conducted a study on Black-shouldered Kite’s nesting biology in Carey Island, Selangor, Malaysia. We divided the island into six types of habitat and conducted road-side count of Black-shouldered Kite from April 2009 to February 2011. Whenever the Black-shouldered Kite was detected, we thoroughly searched the surrounding area for their nest. In total, we have recorded forty nests. The nests were built on 15 species of trees but most of the trees shared common physical characteristics. Some novice breeders also used oil palm tree as their nesting site. Structure and building materials of nests constructed on oil palm trees were different from nests built on other trees. Of all breeding attempts, only four nests which were located in residential area adjacent to young oil palm habitat were successful. Among important characteristics of successful nesting site include taller trees with strong branches and good leaf coverage. These trees not only protect nests from predator detection (except from other predatory birds and physical environment but also facilitate Black-shouldered Kite’s foraging activities by providing good vantage point. Keywords: Road-side counts, Direct observation, Breeding raptors, Nesting tree, Habitat selection

  14. Effect of woodland patch size on rodent seed predation in a fragmented landscape

    Directory of Open Access Journals (Sweden)

    J. Loman

    2007-05-01

    Full Text Available Predation on large woody plant seeds; chestnuts, acorns and sloe kernels, was studied in deciduous forests of two size classes: small woodlots (<1 ha and large woods (at least 25 ha in southern Sweden. Seeds used for the study were artificially distributed on the forest ground and seed predation measured as seed removal. Predation rate was similar in both types of woods. However, rodent density was higher in small woodlots and a correction for differences in rodent density showed that predation rate per individual rodent was higher in the large woods. This suggests that the small woodlots (including the border zone and their adjacent fields have more rodent food per area unit. A small woodlot cannot be considered a representative sample of a large continuous forest, even if the habitats appear similar. There was a strong effect of rodent density on seed predation rate. This suggests that rodents are major seed predators in this habitat.

  15. Fasting or fear: disentangling the roles of predation risk and food deprivation in the nitrogen metabolism of consumers.

    Science.gov (United States)

    Dalton, Christopher M; Tracy, Karen E; Hairston, Nelson G; Flecker, Alexander S

    2018-03-01

    Predators can alter nutrient cycles simply by inducing stress in prey. This stress accelerates prey's protein catabolism, nitrogen waste production, and nitrogen cycling. Yet predators also reduce the feeding rates of their prey, inducing food deprivation that is expected to slow protein catabolism and nitrogen cycling. The physiology of prey under predation risk thus balances the influences of predation risk and food deprivation, and this balance is central to understanding the role of predators in nutrient cycles. We explored the separate and combined effects of predation risk and food deprivation on prey physiology and nutrient cycling by exposing guppies (Poecilia reticulata) to predation risk and food deprivation in a 2 × 2 design. We simulated predation risk using chemical cues from a natural predator of guppies, and we created food deprivation by rationing food availability. We measured guppy response as food consumption, growth, tissue energy density, tissue carbon:nitrogen, and nitrogen (N) excretion and assimilation. We found that N-linked physiological processes (N consumption, assimilation, excretion) were strongly affected by predation risk, independent of food consumption. Guppies excreted substantially less under predation risk than they did under food deprivation or control conditions. These results suggest that predation risk, per se, triggers physiological changes in guppies that increase N retention and decrease N excretion. We suggest that slower N metabolism under predation risk is an adaptive response that minimizes protein loss in the face of predictable, predator-induced food restriction. Notably, N metabolism shares common hormonal control with food seeking behavior, and we speculate that increased N retention is a direct and immediate result of reduced food seeking under predation risk. Contrary to predation-stress-based hypotheses for how predators affect nutrient cycling by prey, our result indicates that even short-term exposure to predators

  16. A potential predator-prey interaction of an American badger and an Agassiz's desert tortoise with a review of badger predation on turtles

    Science.gov (United States)

    Smith, Amanda L.; Puffer, Shellie R.; Lovich, Jeffrey E.; Tennant, Laura A.; Arundel, Terry; Vamstad, Michael S.; Brundige, Kathleen D.

    2016-01-01

    The federally threatened Agassiz’s desert tortoise (Gopherus agassizii) was listed under the U.S. Endangered Species Act in 1990, but thus far, recovery efforts have been unsuccessful (U.S. Fish and Wildlife Service [USFWS] 2015). Predation has been identified as a contributing factor to declining G. agassizii populations range-wide (e.g., Esque et al. 2010, Lovich et al. 2014). Understanding and managing for predator-prey dynamics is thus an important part of the recovery and conservation of this threatened species (USFWS 2011). Desert tortoises have a host of predators at all stages of their life cycle. Over 20 species of birds, mammals, and reptiles have been recorded as known or suspected predators (Woodbury and Hardy 1948, Luckenbach 1982, Ernst and Lovich 2009). American badgers (Taxidea taxus, family: Mustelidae) are confirmed excavators of desert tortoise nests (Turner and Berry 1984). They are also suspected predators of adult desert tortoises, a possibility which has been presented in some studies but without empirical verification (Luckenbach 1982, Turner and Berry 1984). Active mostly at night, badgers are solitary, secretive predators (Lindzey 1978, 1982; Armitage 2004) that are extremely difficult to observe in predatory encounters. Recently, strong circumstantial evidence presented by Emblidge et al. (2015) suggests that badgers do prey on adult Agassiz’s desert tortoises based on observations of more than two dozen dead tortoises in the Western Mojave Desert of California. In this note, we present another case of potential badger predation on a large adult desert tortoise in the Sonoran Desert of California. Collectively, these recent two cases potentially indicate that badger predation may be more common and widespread than previously thought. In addition, we review the worldwide literature of badger predation on turtles in general and summarize reported badger observations in Joshua Tree National Park, where our observation occurred, over a

  17. Selection of anthropogenic features and vegetation characteristics by nesting Common Ravens in the sagebrush ecosystem

    Science.gov (United States)

    Howe, Kristy B.; Coates, Peter S.; Delehanty, David J.

    2014-01-01

    Common Raven (Corvus corax) numbers and distribution are increasing throughout the sagebrush steppe, influencing avian communities in complex ways. Anthropogenic structures are thought to increase raven populations by providing food and nesting subsidies, which is cause for concern because ravens are important nest predators of sensitive species, including Greater Sage-Grouse (Centrocercus urophasianus). During 2007–2009, we located raven nests in southeastern Idaho and conducted a resource selection analysis. We measured variables at multiple spatial scales for 72 unique nest locations, including landscape-level vegetation characteristics and anthropogenic structures. Using generalized linear mixed models and an information-theoretic approach, we found a 31% decrease in the odds of nesting by ravens for every 1 km increase in distance away from a transmission line. Furthermore, a 100-m increase in distance away from the edge of two different land cover types decreased the odds of nesting by 20%, and an increase in the amount of edge by 1 km within an area of 102.1 ha centered on the nest increased the odds of nesting by 49%. A post hoc analysis revealed that ravens were most likely to nest near edges of adjoining big sagebrush (Artemisia tridentata) and land cover types that were associated with direct human disturbance or fire. These findings contribute to our understanding of raven expansion into rural environments and could be used to make better-informed conservation decisions, especially in the face of increasing renewable energy development.

  18. Nested trampoline resonators for optomechanics

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, M. J., E-mail: mweaver@physics.ucsb.edu; Pepper, B.; Luna, F.; Perock, B. [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Buters, F. M.; Eerkens, H. J.; Welker, G.; Heeck, K.; Man, S. de [Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, 2333 CA Leiden (Netherlands); Bouwmeester, D. [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, 2333 CA Leiden (Netherlands)

    2016-01-18

    Two major challenges in the development of optomechanical devices are achieving a low mechanical and optical loss rate and vibration isolation from the environment. We address both issues by fabricating trampoline resonators made from low pressure chemical vapor deposition Si{sub 3}N{sub 4} with a distributed Bragg reflector mirror. We design a nested double resonator structure with 80 dB of mechanical isolation from the mounting surface at the inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower frequencies in agreement with the design. We reliably fabricate devices with mechanical quality factors of around 400 000 at room temperature. In addition, these devices were used to form optical cavities with finesse up to 181 000 ± 1000. These promising parameters will enable experiments in the quantum regime with macroscopic mechanical resonators.

  19. Nested trampoline resonators for optomechanics

    International Nuclear Information System (INIS)

    Weaver, M. J.; Pepper, B.; Luna, F.; Perock, B.; Buters, F. M.; Eerkens, H. J.; Welker, G.; Heeck, K.; Man, S. de; Bouwmeester, D.

    2016-01-01

    Two major challenges in the development of optomechanical devices are achieving a low mechanical and optical loss rate and vibration isolation from the environment. We address both issues by fabricating trampoline resonators made from low pressure chemical vapor deposition Si 3 N 4 with a distributed Bragg reflector mirror. We design a nested double resonator structure with 80 dB of mechanical isolation from the mounting surface at the inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower frequencies in agreement with the design. We reliably fabricate devices with mechanical quality factors of around 400 000 at room temperature. In addition, these devices were used to form optical cavities with finesse up to 181 000 ± 1000. These promising parameters will enable experiments in the quantum regime with macroscopic mechanical resonators

  20. Nested trampoline resonators for optomechanics

    Science.gov (United States)

    Weaver, M. J.; Pepper, B.; Luna, F.; Buters, F. M.; Eerkens, H. J.; Welker, G.; Perock, B.; Heeck, K.; de Man, S.; Bouwmeester, D.

    2016-01-01

    Two major challenges in the development of optomechanical devices are achieving a low mechanical and optical loss rate and vibration isolation from the environment. We address both issues by fabricating trampoline resonators made from low pressure chemical vapor deposition Si3N4 with a distributed Bragg reflector mirror. We design a nested double resonator structure with 80 dB of mechanical isolation from the mounting surface at the inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower frequencies in agreement with the design. We reliably fabricate devices with mechanical quality factors of around 400 000 at room temperature. In addition, these devices were used to form optical cavities with finesse up to 181 000 ± 1000. These promising parameters will enable experiments in the quantum regime with macroscopic mechanical resonators.

  1. No evidence for UV-based nest-site selection in sticklebacks

    Directory of Open Access Journals (Sweden)

    Bakker Theo CM

    2006-11-01

    Full Text Available Abstract Background Nests are built in various animal taxa including fish. In systems with exclusive male parental care, the choice of a nest site may be an important component of male fitness. The nest site may influence male attractiveness as a mate, and male, embryo, and juvenile survival probabilities. Reproductively active three-spined stickleback males establish and defend a territory in which they build a nest. Territories can differ remarkably in qualities that influence male and female reproductive success like predation risk or abiotic factors such as dissolved oxygen concentration or lighting conditions. The latter may be important because in sticklebacks the extended visual capability into the ultraviolet (UV wave range plays a role in female mate choice. Males are thus expected to be choosy about the habitat in which they will build their nest. Results We tested nest-site choice in male three-spined sticklebacks with respect to different UV lighting conditions. Reproductively active males were given the simultaneous choice to build their nest either in an UV-rich (UV+ or an UV-lacking (UV- environment. Males exhibited no significant nest-site preferences with respect to UV+ or UV-. However, larger males and also heavier ones completed their nests earlier. Conclusion We found that UV radiation as well as differences in luminance had no influence on nest-site choice in three-spined sticklebacks. Males that built in the UV-rich environment were not different in any trait (body traits and UV reflection traits from males that built in the UV-poor environment. There was a significant effect of standard length and body mass on the time elapsed until nest completion in the UV experiment. The larger and heavier a male, the faster he completed his nest. In the brightness control experiment there was a significant effect only of body mass on the duration of nest completion. Whether nest building preferences with respect to UV lighting

  2. Habitat fragmentation reduces nest survival in an Afrotropical bird community in a biodiversity hotspot.

    Science.gov (United States)

    Newmark, William D; Stanley, Thomas R

    2011-07-12

    Ecologists have long hypothesized that fragmentation of tropical landscapes reduces avian nest success. However, this hypothesis has not been rigorously assessed because of the difficulty of finding large numbers of well-hidden nests in tropical forests. Here we report that in the East Usambara Mountains in Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot, that daily nest survival rate and nest success for seven of eight common understory bird species that we examined over a single breeding season were significantly lower in fragmented than in continuous forest, with the odds of nest failure for these seven species ranging from 1.9 to 196.8 times higher in fragmented than continuous forest. Cup-shaped nests were particularly vulnerable in fragments. We then examined over six breeding seasons and 14 study sites in a multivariable survival analysis the influence of landscape structure and nest location on daily nest survival for 13 common species representing 1,272 nests and four nest types (plate, cup, dome, and pouch). Across species and nest types, area, distance of nest to edge, and nest height had a dominant influence on daily nest survival, with area being positively related to nest survival and distance of nest to edge and nest height being both positively and negatively associated with daily nest survival. Our results indicate that multiple environmental factors contribute to reduce nest survival within a tropical understory bird community in a fragmented landscape and that maintaining large continuous forest is important for enhancing nest survival for Afrotropical understory birds.

  3. Intelligent nesting system

    Directory of Open Access Journals (Sweden)

    Đuričić Zoran

    2003-01-01

    Full Text Available The economy of the process for the manufacture of parts from sheet metal plates depends on successful solution of the process of cutting various parts from sheet metal plates. Essentially, the problem is to arrange contours within a defined space so that they take up minimal surface. When taken in this way, the considered problem assumes a more general nature; it refers to the utilization of a flat surface, and it can represent a general principle of arranging 2D contours on a certain surface. The paper presents a conceptual solution and a prototypal intelligent nesting system for optimal cutting. The problem of nesting can generally be divided into two intellectual phases: recognition and classification of shapes, and arrangement of recognized shapes on a given surface. In solving these problems, methods of artificial intelligence are applied. In the paper, trained neural network is used for recognition of shapes; on the basis of raster record of a part's drawing, it recognizes the part's shape and which class it belongs to. By means of the expert system, based on rules defined on the basis of acquisition of knowledge from manufacturing sections, as well as on the basis of certain mathematical algorithms, parts are arranged on the arrangement surface. Both systems can also work independently, having been built on the modular principle. The system uses various product models as elements of integration for the entire system. .

  4. Neste plans three projects

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Neste Chemicals (Helsinki) is discussing three joint ventures with local authorities in China, says Mikko Haapavaara, v.p./Asia. The projects should help the Finnish producer to increase sales in Asia by a considerable amount by 2000, he says. The plan involves production of polyethylene (PE), unsaturated polyester resins and PE compounding-all core operations. Sites have not been selected, but Shanghai is the favored location for the PE operations. The company is also looking at a site in the south, near Hong Kong, and at locations near Beijing. The PE plant would need to be near an ethylene unit, says Haapavaara. The PE resin plant would be designed to produce about 150,000 m.t./year and would cost about No. 150 million. A part of the output would need to be exported to take care of the financing, the company says. A feasibility study now under way with the potential Chinese partners should be completed by the end of March. The plant would use Neste's linear low-density PE process, proved in a world-scale plant at Beringen, Belgium. The compounding units would produce specialty PE material for the wire and cable and pipe industry. The company is a joint venture partner in a propane dehydrogenation/polypropylene (PP) plant and a minority partner in a Qualipoly, the 20,000 m.t./year unsaturated polyester resin producer

  5. PyNEST: a convenient interface to the NEST simulator

    Directory of Open Access Journals (Sweden)

    Jochen M Eppler

    2009-01-01

    Full Text Available The neural simulation tool NEST (http://www.nest-initiative.org is a simulator for heterogeneous networks of point neurons or neurons with a small number of compartments. It aims at simulations of large neural systems with more than 10^4 neurons and 10^7 to 10^9 synapses. NEST is implemented in C++ and can be used on a large range of architectures from single-core laptops over multi-core desktop computers to super-computers with thousands of processor cores. Python (http://www.python.org is a modern programming language that has recently received considerable attention in Computational Neuroscience. Python is easy to learn and has many extension modules for scientific computing (e.g. http://www.scipy.org. In this contribution we describe PyNEST, the new user interface to NEST. PyNEST combines NEST’s efficient simulation kernel with the simplicity and flexibility of Python. Compared to NEST’s native simulation language SLI, PyNEST makes it easier to set up simulations, generate stimuli, and analyze simulation results. We describe how PyNEST connects NEST and Python and how it is implemented. With a number of examples, we illustrate how it is used.

  6. Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

    Science.gov (United States)

    Seamone, Scott; Blaine, Tristan; Higham, Timothy E

    2014-12-01

    Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach. Copyright © 2014 Elsevier GmbH. All rights reserved.

  7. Relationship between snow depth and gray wolf predation on white-tailed deer

    Science.gov (United States)

    Nelson, M.E.; Mech, L.D.

    1986-01-01

    Survival of 203 yearling and adult white-tailed deer (Odocoileus virginianus) was monitored for 23,441 deer days from January through April 1975-85 in northeastern Minnesota. Gray wolf (Canis lupus) predation was the primary mortality cause, and from year to year during this period, the mean predation rate ranged from 0.00 to 0.29. The sum of weekly snow depths/month explained 51% of the variation in annual wolf predation rate, with the highest predation during the deepest snow.

  8. Nesting behavior of Palila, as assessed from video recordings

    Science.gov (United States)

    Laut, M.E.; Banko, P.C.; Gray, E.M.

    2003-01-01

    We quantified nesting behavior of Palila (Loxiodes bailleui), an endangered Hawaiian honeycreeper, by recording at nests during three breeding seasons using a black-and-white video camera connected to a Videocassette recorder. A total of seven nests was observed. We measured the following factors for daylight hours: percentage of time the female was on the nest (attendance), length of attendance bouts by the female, length of nest recesses, and adult provisioning rates. Comparisons were made between three stages of the 40-day nesting cycle: incubation (day 1-day 16), early nestling stage (day 17-day 30 [i.e., nestlings ??? 14 days old]), and late nestling stage (day 31-day 40 [i.e., nestlings > 14 days old]). Of seven nests observed, four fledged at least one nestling and three failed. One of these failed nests was filmed being depredated by a feral cat (Felis catus). Female nest attendance was near 82% during the incubation stage and decreased to 21% as nestlings aged. We did not detect a difference in attendance bout length between stages of the nesting cycle. Mean length of nest recesses increased from 4.5 min during the incubation stage to over 45 min during the late nestling stage. Mean number of nest recesses per hour ranged from 1.6 to 2.0. Food was delivered to nestlings by adults an average of 1.8 times per hour for the early nestling stage and 1.5 times per hour during the late nestling stage and did not change over time. Characterization of parental behavior by video had similarities to but also key differences from findings taken from blind observations. Results from this study will facilitate greater understanding of Palila reproductive strategies.

  9. Biomechanics of predator-prey arms race in lion, zebra, cheetah and impala

    Science.gov (United States)

    Wilson, Alan M.; Hubel, Tatjana Y.; Wilshin, Simon D.; Lowe, John C.; Lorenc, Maja; Dewhirst, Oliver P.; Bartlam-Brooks, Hattie L. A.; Diack, Rebecca; Bennitt, Emily; Golabek, Krystyna A.; Woledge, Roger C.; McNutt, J. Weldon; Curtin, Nancy A.; West, Timothy G.

    2018-02-01

    The fastest and most manoeuvrable terrestrial animals are found in savannah habitats, where predators chase and capture running prey. Hunt outcome and success rate are critical to survival, so both predator and prey should evolve to be faster and/or more manoeuvrable. Here we compare locomotor characteristics in two pursuit predator-prey pairs, lion-zebra and cheetah-impala, in their natural savannah habitat in Botswana. We show that although cheetahs and impalas were universally more athletic than lions and zebras in terms of speed, acceleration and turning, within each predator-prey pair, the predators had 20% higher muscle fibre power than prey, 37% greater acceleration and 72% greater deceleration capacity than their prey. We simulated hunt dynamics with these data and showed that hunts at lower speeds enable prey to use their maximum manoeuvring capacity and favour prey survival, and that the predator needs to be more athletic than its prey to sustain a viable success rate.

  10. Giant honeybees ( Apis dorsata) mob wasps away from the nest by directed visual patterns

    Science.gov (United States)

    Kastberger, Gerald; Weihmann, Frank; Zierler, Martina; Hötzl, Thomas

    2014-11-01

    The open nesting behaviour of giant honeybees ( Apis dorsata) accounts for the evolution of a series of defence strategies to protect the colonies from predation. In particular, the concerted action of shimmering behaviour is known to effectively confuse and repel predators. In shimmering, bees on the nest surface flip their abdomens in a highly coordinated manner to generate Mexican wave-like patterns. The paper documents a further-going capacity of this kind of collective defence: the visual patterns of shimmering waves align regarding their directional characteristics with the projected flight manoeuvres of the wasps when preying in front of the bees' nest. The honeybees take here advantage of a threefold asymmetry intrinsic to the prey-predator interaction: (a) the visual patterns of shimmering turn faster than the wasps on their flight path, (b) they "follow" the wasps more persistently (up to 100 ms) than the wasps "follow" the shimmering patterns (up to 40 ms) and (c) the shimmering patterns align with the wasps' flight in all directions at the same strength, whereas the wasps have some preference for horizontal correspondence. The findings give evidence that shimmering honeybees utilize directional alignment to enforce their repelling power against preying wasps. This phenomenon can be identified as predator driving which is generally associated with mobbing behaviour (particularly known in selfish herds of vertebrate species), which is, until now, not reported in insects.

  11. Turbidity interferes with foraging success of visual but not chemosensory predators.

    Science.gov (United States)

    Lunt, Jessica; Smee, Delbert L

    2015-01-01

    Predation can significantly affect prey populations and communities, but predator effects can be attenuated when abiotic conditions interfere with foraging activities. In estuarine communities, turbidity can affect species richness and abundance and is changing in many areas because of coastal development. Many fish species are less efficient foragers in turbid waters, and previous research revealed that in elevated turbidity, fish are less abundant whereas crabs and shrimp are more abundant. We hypothesized that turbidity altered predatory interactions in estuaries by interfering with visually-foraging predators and prey but not with organisms relying on chemoreception. We measured the effects of turbidity on the predation rates of two model predators: a visual predator (pinfish, Lagodon rhomboides) and a chemosensory predator (blue crabs, Callinectes sapidus) in clear and turbid water (0 and ∼100 nephelometric turbidity units). Feeding assays were conducted with two prey items, mud crabs (Panopeus spp.) that rely heavily on chemoreception to detect predators, and brown shrimp (Farfantepenaus aztecus) that use both chemical and visual cues for predator detection. Because turbidity reduced pinfish foraging on both mud crabs and shrimp, the changes in predation rates are likely driven by turbidity attenuating fish foraging ability and not by affecting prey vulnerability to fish consumers. Blue crab foraging was unaffected by turbidity, and blue crabs were able to successfully consume nearly all mud crab and shrimp prey. Turbidity can influence predator-prey interactions by reducing the feeding efficiency of visual predators, providing a competitive advantage to chemosensory predators, and altering top-down control in food webs.

  12. Nesting biology of Black-shouldered Kite (Elanus caeruleus) in oil palm landscape in Carey Island, Peninsular Malaysia.

    Science.gov (United States)

    Ramli, Rosli; Fauzi, Aimi

    2018-03-01

    Black-shouldered Kite ( Elanus caeruleus ) is a well-known raptor that inhabits open areas such as oil palm plantation or paddy field. To determine preferable habitat and nesting site of Black-shouldered Kite in oil palm landscape, we conducted a study on Black-shouldered Kite's nesting biology in Carey Island, Selangor, Malaysia. We divided the island into six types of habitat and conducted road-side count of Black-shouldered Kite from April 2009 to February 2011. Whenever the Black-shouldered Kite was detected, we thoroughly searched the surrounding area for their nest. In total, we have recorded forty nests. The nests were built on 15 species of trees but most of the trees shared common physical characteristics. Some novice breeders also used oil palm tree as their nesting site. Structure and building materials of nests constructed on oil palm trees were different from nests built on other trees. Of all breeding attempts, only four nests which were located in residential area adjacent to young oil palm habitat were successful. Among important characteristics of successful nesting site include taller trees with strong branches and good leaf coverage. These trees not only protect nests from predator detection (except from other predatory birds) and physical environment but also facilitate Black-shouldered Kite's foraging activities by providing good vantage point.

  13. Trap Nesting Wasps and Bees in Agriculture: A Comparison of Sown Wildflower and Fallow Plots in Florida.

    Science.gov (United States)

    Campbell, Joshua W; Smithers, Cherice; Irvin, Allyn; Kimmel, Chase B; Stanley-Stahr, Cory; Daniels, Jaret C; Ellis, James D

    2017-10-10

    Wildflower strip plantings in intensive agricultural systems have become a widespread tool for promoting pollination services and biological conservation because of their use by wasps and bees. Many of the trap-nesting wasps are important predators of common crop pests, and cavity-nesting bees that utilize trap-nests are important pollinators for native plants and many crops. The impact of wildflower strips on the nesting frequency of trap-nesting wasps or bees within localized areas has not been thoroughly investigated. Trap-nests made of bamboo reeds ( Bambusa sp.) were placed adjacent to eight 0.1 ha wildflower plots and paired fallow areas (control plots) to determine if wildflower strips encourage the nesting of wasps and bees. From August 2014 to November 2015, occupied reeds were gathered and adults were collected as they emerged from the trap-nests. Treatment (wildflower or fallow plots) did not impact the number of occupied reeds or species richness of trap-nesting wasps using the occupied reeds. The wasps Pachodynerus erynnis , Euodynerus megaera , Parancistrocerus pedestris , and Isodontia spp. were the most common trap-nesting species collected. Less than 2% of the occupied reeds contained bees, and all were from the genus Megachile . The nesting wasp and bee species demonstrated preferences for reeds with certain inside diameters (IDs). The narrow range of ID preferences exhibited by each bee/wasp may provide opportunities to take advantage of their natural histories for biological control and/or pollination purposes.

  14. Trap Nesting Wasps and Bees in Agriculture: A Comparison of Sown Wildflower and Fallow Plots in Florida

    Directory of Open Access Journals (Sweden)

    Joshua W. Campbell

    2017-10-01

    Full Text Available Wildflower strip plantings in intensive agricultural systems have become a widespread tool for promoting pollination services and biological conservation because of their use by wasps and bees. Many of the trap-nesting wasps are important predators of common crop pests, and cavity-nesting bees that utilize trap-nests are important pollinators for native plants and many crops. The impact of wildflower strips on the nesting frequency of trap-nesting wasps or bees within localized areas has not been thoroughly investigated. Trap-nests made of bamboo reeds (Bambusa sp. were placed adjacent to eight 0.1 ha wildflower plots and paired fallow areas (control plots to determine if wildflower strips encourage the nesting of wasps and bees. From August 2014 to November 2015, occupied reeds were gathered and adults were collected as they emerged from the trap-nests. Treatment (wildflower or fallow plots did not impact the number of occupied reeds or species richness of trap-nesting wasps using the occupied reeds. The wasps Pachodynerus erynnis, Euodynerus megaera, Parancistrocerus pedestris, and Isodontia spp. were the most common trap-nesting species collected. Less than 2% of the occupied reeds contained bees, and all were from the genus Megachile. The nesting wasp and bee species demonstrated preferences for reeds with certain inside diameters (IDs. The narrow range of ID preferences exhibited by each bee/wasp may provide opportunities to take advantage of their natural histories for biological control and/or pollination purposes.

  15. Nesting ecology of boreal forest birds following a massive outbreak of spruce beetles

    Science.gov (United States)

    Matsuoka, S.M.; Handel, C.M.

    2007-01-01

    We studied breeding dark-eyed juncos (Junco hyemalis), yellow-rumped warblers (Dendroica coronata), and spruce-nesting birds from 1997 to 1998 among forests with different levels of spruce (Picea spp.) mortality following an outbreak of spruce beetles (Dendroctonus rufipennis) in Alaska, USA. We identified species using live and beetle-killed spruce for nest sites and monitored nests to determine how the outbreak influenced avian habitat selection and reproduction. We tested predictions that 1) nesting success of ground-nesting juncos would increase with spruce mortality due to proliferation of understory vegetation available to conceal nests from predators, 2) nesting success of canopy-nesting warblers would decrease with spruce mortality due to fewer live spruce in which to conceal nests, and 3) both species would alter nest-site selection in response to disturbance. Juncos did not benefit from changes in understory vegetation; nesting success in highly disturbed stands (46%) was comparable to that in undisturbed habitats throughout their range. In stands with low spruce mortality, nesting success of juncos was low (5%) and corresponded with high densities of red squirrels (Tamiasciurus hudsonicus). Yellow-rumped warblers nested exclusively in spruce, but success did not vary with spruce mortality. As disturbance increased, nesting warblers switched from selecting forest patches with high densities of live white spruce (Picea glauca) to patches with beetle-killed spruce. Warblers also placed nests in large-diameter live or beetle-killed spruce, depending on which was more abundant in the stand, with no differences in nesting success. Five of the 12 other species of spruce-nesting birds also used beetle-killed spruce as nest sites. Because beetle-killed spruce can remain standing for >50 years, even highly disturbed stands provide an important breeding resource for boreal forest birds. We recommend that boreal forest managers preserve uncut blocks of infested

  16. Nest trampling and ground nesting birds: Quantifying temporal and spatial overlap between cattle activity and breeding redshank.

    Science.gov (United States)

    Sharps, Elwyn; Smart, Jennifer; Mason, Lucy R; Jones, Kate; Skov, Martin W; Garbutt, Angus; Hiddink, Jan G

    2017-08-01

    Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low-intensity grazing at nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications : Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid

  17. Evolution determines how global warming and pesticide exposure will shape predator-prey interactions with vector mosquitoes.

    Science.gov (United States)

    Tran, Tam T; Janssens, Lizanne; Dinh, Khuong V; Op de Beeck, Lin; Stoks, Robby

    2016-07-01

    How evolution may mitigate the effects of global warming and pesticide exposure on predator-prey interactions is directly relevant for vector control. Using a space-for-time substitution approach, we addressed how 4°C warming and exposure to the pesticide endosulfan shape the predation on Culex pipiens mosquitoes by damselfly predators from replicated low- and high-latitude populations. Although warming was only lethal for the mosquitoes, it reduced predation rates on these prey. Possibly, under warming escape speeds of the mosquitoes increased more than the attack efficiency of the predators. Endosulfan imposed mortality and induced behavioral changes (including increased filtering and thrashing and a positional shift away from the bottom) in mosquito larvae. Although the pesticide was only lethal for the mosquitoes, it reduced predation rates by the low-latitude predators. This can be explained by the combination of the evolution of a faster life history and associated higher vulnerabilities to the pesticide (in terms of growth rate and lowered foraging activity) in the low-latitude predators and pesticide-induced survival selection in the mosquitoes. Our results suggest that predation rates on mosquitoes at the high latitude will be reduced under warming unless predators evolve toward the current low-latitude phenotype or low-latitude predators move poleward.

  18. Regional drivers of clutch loss reveal important trade-offs for beach-nesting birds.

    Science.gov (United States)

    Maslo, Brooke; Schlacher, Thomas A; Weston, Michael A; Huijbers, Chantal M; Anderson, Chris; Gilby, Ben L; Olds, Andrew D; Connolly, Rod M; Schoeman, David S

    2016-01-01

    Coastal birds are critical ecosystem constituents on sandy shores, yet are threatened by depressed reproductive success resulting from direct and indirect anthropogenic and natural pressures. Few studies examine clutch fate across the wide range of environments experienced by birds; instead, most focus at the small site scale. We examine survival of model shorebird clutches as an index of true clutch survival at a regional scale (∼200 km), encompassing a variety of geomorphologies, predator communities, and human use regimes in southeast Queensland, Australia. Of the 132 model nests deployed and monitored with cameras, 45 (34%) survived the experimental exposure period. Thirty-five (27%) were lost to flooding, 32 (24%) were depredated, nine (7%) buried by sand, seven (5%) destroyed by people, three (2%) failed by unknown causes, and one (1%) was destroyed by a dog. Clutch fate differed substantially among regions, particularly with respect to losses from flooding and predation. 'Topographic' exposure was the main driver of mortality of nests placed close to the drift line near the base of dunes, which were lost to waves (particularly during storms) and to a lesser extent depredation. Predators determined the fate of clutches not lost to waves, with the depredation probability largely influenced by region. Depredation probability declined as nests were backed by higher dunes and were placed closer to vegetation. This study emphasizes the scale at which clutch fate and survival varies within a regional context, the prominence of corvids as egg predators, the significant role of flooding as a source of nest loss, and the multiple trade-offs faced by beach-nesting birds and those that manage them.

  19. Regional drivers of clutch loss reveal important trade-offs for beach-nesting birds

    Directory of Open Access Journals (Sweden)

    Brooke Maslo

    2016-09-01

    Full Text Available Coastal birds are critical ecosystem constituents on sandy shores, yet are threatened by depressed reproductive success resulting from direct and indirect anthropogenic and natural pressures. Few studies examine clutch fate across the wide range of environments experienced by birds; instead, most focus at the small site scale. We examine survival of model shorebird clutches as an index of true clutch survival at a regional scale (∼200 km, encompassing a variety of geomorphologies, predator communities, and human use regimes in southeast Queensland, Australia. Of the 132 model nests deployed and monitored with cameras, 45 (34% survived the experimental exposure period. Thirty-five (27% were lost to flooding, 32 (24% were depredated, nine (7% buried by sand, seven (5% destroyed by people, three (2% failed by unknown causes, and one (1% was destroyed by a dog. Clutch fate differed substantially among regions, particularly with respect to losses from flooding and predation. ‘Topographic’ exposure was the main driver of mortality of nests placed close to the drift line near the base of dunes, which were lost to waves (particularly during storms and to a lesser extent depredation. Predators determined the fate of clutches not lost to waves, with the depredation probability largely influenced by region. Depredation probability declined as nests were backed by higher dunes and were placed closer to vegetation. This study emphasizes the scale at which clutch fate and survival varies within a regional context, the prominence of corvids as egg predators, the significant role of flooding as a source of nest loss, and the multiple trade-offs faced by beach-nesting birds and those that manage them.

  20. Animal behaviour and algal camouflage jointly structure predation and selection.

    Science.gov (United States)

    Start, Denon

    2018-05-01

    Trait variation can structure interactions between individuals, thus shaping selection. Although antipredator strategies are an important component of many aquatic systems, how multiple antipredator traits interact to influence consumption and selection remains contentious. Here, I use a common larval dragonfly (Epitheca canis) and its predator (Anax junius) to test for the joint effects of activity rate and algal camouflage on predation and survival selection. I found that active and poorly camouflaged Epitheca were more likely to be consumed, and thus, survival selection favoured inactive and well-camouflaged individuals. Notably, camouflage dampened selection on activity rate, likely by reducing attack rates when Epitheca encountered a predator. Correlational selection is therefore conferred by the ecological interaction of traits, rather than by opposing selection acting on linked traits. I suggest that antipredator traits with different adaptive functions can jointly structure patterns of consumption and selection. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

  1. Predation vulnerability of planktonic copepods: consequences of predator foraging strategies and prey sensory abilities

    DEFF Research Database (Denmark)

    Viitasalo, M; Kiørboe, T; Flinkman, J.

    1998-01-01

    We investigated the vulnerability of 2 copepod species (Eurytemora affinis and Temora longicornis) to predation by predators with different foraging modes, three-spined stickleback Gasterosteus aculeatus juveniles and mysid shrimps Neomysis integer. Copepods were videofilmed escaping from predators...

  2. Physical and biochemical changes in sludge upon Tubifex tubifex predation

    NARCIS (Netherlands)

    de Valk, S.L.; Khadem, A.F.; Foreman, Christine M.; van Lier, J.B.; de Kreuk, M.K.

    2016-01-01

    Worm predation (WP) on activated sludge leads to increased sludge degradation rates, irrespective of the type of worm used or reactor conditions employed. However, the cause of the increased sludge degradation rates remains unknown. This paper presents a comparative analysis of the physical and

  3. Detection probabilities of woodpecker nests in mixed conifer forests in Oregon

    Science.gov (United States)

    Robin E. Russell; Victoria A. Saab; Jay J. Rotella; Jonathan G. Dudley

    2009-01-01

    Accurate estimates of Black-backed (Picoides arcticus) and Hairy Woodpecker (P. villosus) nests and nest survival rates in post-fire landscapes provide land managers with information on the relative importance of burned forests to nesting woodpeckers. We conducted multiple-observer surveys in burned and unburned mixed coniferous forests in Oregon to identify important...

  4. Predators on private land: broad-scale socioeconomic interactions influence large predator management

    Directory of Open Access Journals (Sweden)

    Hayley S. Clements

    2016-06-01

    Full Text Available The proliferation of private land conservation areas (PLCAs is placing increasing pressure on conservation authorities to effectively regulate their ecological management. Many PLCAs depend on tourism for income, and charismatic large mammal species are considered important for attracting international visitors. Broad-scale socioeconomic factors therefore have the potential to drive fine-scale ecological management, creating a systemic scale mismatch that can reduce long-term sustainability in cases where economic and conservation objectives are not perfectly aligned. We assessed the socioeconomic drivers and outcomes of large predator management on 71 PLCAs in South Africa. Owners of PLCAs that are stocking free-roaming large predators identified revenue generation as influencing most or all of their management decisions, and rated profit generation as a more important objective than did the owners of PLCAs that did not stock large predators. Ecotourism revenue increased with increasing lion (Panthera leo density, which created a potential economic incentive for stocking lion at high densities. Despite this potential mismatch between economic and ecological objectives, lion densities were sustainable relative to available prey. Regional-scale policy guidelines for free-roaming lion management were ecologically sound. By contrast, policy guidelines underestimated the area required to sustain cheetah (Acinonyx jubatus, which occurred at unsustainable densities relative to available prey. Evidence of predator overstocking included predator diet supplementation and frequent reintroduction of game. We conclude that effective facilitation of conservation on private land requires consideration of the strong and not necessarily beneficial multiscale socioeconomic factors that influence private land management.

  5. Climate change and nesting behaviour in vertebrates: a review of the ecological threats and potential for adaptive responses.

    Science.gov (United States)

    Mainwaring, Mark C; Barber, Iain; Deeming, Denis C; Pike, David A; Roznik, Elizabeth A; Hartley, Ian R

    2017-11-01

    Nest building is a taxonomically widespread and diverse trait that allows animals to alter local environments to create optimal conditions for offspring development. However, there is growing evidence that climate change is adversely affecting nest-building in animals directly, for example via sea-level rises that flood nests, reduced availability of building materials, and suboptimal sex allocation in species exhibiting temperature-dependent sex determination. Climate change is also affecting nesting species indirectly, via range shifts into suboptimal nesting areas, reduced quality of nest-building environments, and changes in interactions with nest predators and parasites. The ability of animals to adapt to sustained and rapid environmental change is crucial for the long-term persistence of many species. Many animals are known to be capable of adjusting nesting behaviour adaptively across environmental gradients and in line with seasonal changes, and this existing plasticity potentially facilitates adaptation to anthropogenic climate change. However, whilst alterations in nesting phenology, site selection and design may facilitate short-term adaptations, the ability of nest-building animals to adapt over longer timescales is likely to be influenced by the heritable basis of such behaviour. We urgently need to understand how the behaviour and ecology of nest-building in animals is affected by climate change, and particularly how altered patterns of nesting behaviour affect individual fitness and population persistence. We begin our review by summarising how predictable variation in environmental conditions influences nest-building animals, before highlighting the ecological threats facing nest-building animals experiencing anthropogenic climate change and examining the potential for changes in nest location and/or design to provide adaptive short- and long-term responses to changing environmental conditions. We end by identifying areas that we believe warrant the

  6. Jordan Isomorphisms on Nest Subalgebras

    Directory of Open Access Journals (Sweden)

    Aili Yang

    2015-01-01

    Full Text Available This paper is devoted to the study of Jordan isomorphisms on nest subalgebras of factor von Neumann algebras. It is shown that every Jordan isomorphism ϕ between the two nest subalgebras algMβ and algMγ is either an isomorphism or an anti-isomorphism.

  7. Neste Corporation - a successful year

    International Nuclear Information System (INIS)

    Ihamuotila, J.

    1991-01-01

    The past year proved a successful one for Neste Corporation. Profitability was good and operations were consistently developed. Neste is committed to giving high priority to productivity and know- how to ensure that this success continues into the future. Important developments affecting the structure of Neste Corporation during 1990 included the amalgamation of Neste's oil-related activities into a single division, the increasing concentration of Neste Chemicals, activities in Central and Southern Europe and a major strengthening of oil exploration and production operations. Neste Oil turned in a good result during 1990. Neste imported a total of 8.9 million tonnes of crude oil during 1990. Imports from the Soviet Union at 5.2 million tonnes, were over 2 million tonnes less than planned. Some 2.5 million tonnes were imported from the North Sea, and 1.2 million tonnes from the Middle East. The year was one of expansion, diversification, and solid profit for Neste Chemicals. Net sales grew by 18 % compared to 1989 and the division recorded a satisfactory performance. Petrochemicals and polyolefins production increased suhstantially as a result of plants completed, acquired, or leased during 1989. The gas division's net sales during 1990 were 46 % higher than during 1989. This growth largely resulted from an increase in the consumption of natural gas and an expansion in the volume of international IPG business. The division's profitability remained satisfactory

  8. Differentiated Anti-Predation Responses in a Superorganism.

    Directory of Open Access Journals (Sweden)

    Thomas A O'Shea-Wheller

    Full Text Available Insect societies are complex systems, displaying emergent properties much greater than the sum of their individual parts. As such, the concept of these societies as single 'superorganisms' is widely applied to describe their organisation and biology. Here, we test the applicability of this concept to the response of social insect colonies to predation during a vulnerable period of their life history. We used the model system of house-hunting behaviour in the ant Temnothorax albipennis. We show that removing individuals from directly within the nest causes an evacuation response, while removing ants at the periphery of scouting activity causes the colony to withdraw back into the nest. This suggests that colonies react differentially, but in a coordinated fashion, to these differing types of predation. Our findings lend support to the superorganism concept, as the whole society reacts much like a single organism would in response to attacks on different parts of its body. The implication of this is that a collective reaction to the location of worker loss within insect colonies is key to avoiding further harm, much in the same way that the nervous systems of individuals facilitate the avoidance of localised damage.

  9. Modelling the attack success of planktonic predators: patterns and mechanisms of prey size selectivity

    DEFF Research Database (Denmark)

    Caparroy, P.; Thygesen, Uffe Høgsbro; Visser, Andre

    2000-01-01

    of being captured. By combining the attack success model with previously published hydrodynamic models of predator and prey perception, we examine how predator foraging behaviour and prey perceptive ability affect the size spectra of encountered and captured copepod prey. We examine food size spectra of (i......) a rheotactic cruising predator, (ii) a suspension-feeding hovering copepod and (iii) a larval fish. For rheotactic predators such as carnivorous copepods, a central assumption of the model is that attack is triggered by prey escape reaction, which in turn depends on the deformation rate of the fluid created...

  10. Mourning Dove nesting habitat and nest success in Central Missouri

    Science.gov (United States)

    Drobney, R.D.; Schulz, J.H.; Sheriff, S.L.; Fuemmeler, W.J.

    1998-01-01

    Previous Mourning Dove (Zenaida macroura) nesting studies conducted in areas containing a mixture of edge and continuous habitats have focused on edge habitats. Consequently, little is known about the potential contribution of continuous habitats to dove production. In this study we evaluated the relative importance of these two extensive habitat types by monitoring the habitat use and nest success of 59 radio-marked doves during 1990-1991 in central Missouri. Of 83 nests initiated by our marked sample, most (81.9%) were located in edge habitats. Although continuous habitats were selected less as nest sites, the proportion of successful nests did not differ significantly from that in edge habitats. Our data indicate that continuous habitats should not be considered marginal nesting habitat. If the intensity of use and nest success that we observed are representative regionally or nationally, continuous habitats could contribute substantially to annual Mourning Dove production because of the high availability of these habitats throughout much of the Mourning Dove breeding range.

  11. The Nest Home

    Energy Technology Data Exchange (ETDEWEB)

    Pickerill, Heath [Missouri Univ. of Science and Technology, Rolla, MO (United States)

    2016-07-11

    The purpose of the project was to build a competitive solar-powered house for the U.S. Department of Energy Solar Decathlon 2015 held in Irvine, California. The house, named the Nest Home, was an innovative design that works with the environment to meet the needs of the occupants, identified as a growing family. Reused materials were instrumental in the design. Three refurbished shipping containers composed the primary structure of the house, creating an open floor plan that defies common architecture for container homes. The exterior siding was made of deconstructed shipping pallets collected locally. Other recycled products included carpet composed of discarded fishing nets, denim batting made of recycled blue jeans that outperform traditional fiberglass insulation in sound proofing and thermal resistance, and kitchen cabinets that were purchased used and refinished. Collectively these elements formed a well-balanced blend of modern design, comfort, and sustainability. The house was Missouri University of Science and Technology’s sixth entry in the DOE Solar Decathlon. Missouri S&T has been invited to compete in six of the seven decathlons held, more than any other university worldwide. The house was brought back to Rolla after the Decathlon in California where it has been placed in its permanent location on the S&T campus.

  12. Dark-bellied brent geese Branta b. bernicla breeding near snowy owl Nyctea scandiaca nests lay more and larger eggs

    NARCIS (Netherlands)

    Kleef, H.H. van; Willems, F.; Volkov, A.E.; Smeets, J.H.R.; Nowak, D.; Nowak, A.

    2007-01-01

    Several studies have demonstrated that snowy owls Nyctea scandiaca defend an area around their nests against predators, hereby inadvertently creating safe havens for breeding dark-bellied brent geese Branta b. bernicla. However, studies investigating brent goose breeding ecology within the

  13. Are lemmings prey or predators?

    Science.gov (United States)

    Turchin, P.; Oksanen, L.; Ekerholm, P.; Oksanen, T.; Henttonen, H.

    2000-06-01

    Large oscillations in the populations of Norwegian lemmings have mystified both professional ecologists and lay public. Ecologists suspect that these oscillations are driven by a trophic mechanism: either an interaction between lemmings and their food supply, or an interaction between lemmings and their predators. If lemming cycles are indeed driven by a trophic interaction, can we tell whether lemmings act as the resource (`prey') or the consumer (`predator')? In trophic interaction models, peaks of resource density generally have a blunt, rounded shape, whereas peaks of consumer density are sharp and angular. Here we have applied several statistical tests to three lemming datasets and contrasted them with comparable data for cyclic voles. We find that vole peaks are blunt, consistent with their cycles being driven by the interaction with predators. In contrast, the shape of lemming peaks is consistent with the hypothesis that lemmings are functional predators, that is, their cycles are driven by their interaction with food plants. Our findings suggest that a single mechanism, such as interaction between rodents and predators, is unlikely to provide the `universal' explanation of all cyclic rodent dynamics.

  14. Diets of introduced predators using stable isotopes and stomach contents

    Science.gov (United States)

    Meckstroth, A.M.; Miles, A.K.; Chandra, S.

    2007-01-01

    In a study of predation on ground-nesting birds at South San Francisco Bay (South Bay), California, USA, we analyzed stomach contents and stable isotopes of carbon and nitrogen to identify commonly consumed prey. We obtained the stomach contents from 206 nonnative red foxes (Vulpes vulpes regalis) collected in the South Bay area and Monterey County during 1995-2001 and from 68 feral cats (Felis silvestris) from the South Bay area during 2001-2002. We determined prey identity, biomass, and frequency, described seasonal diet trends, and derived an Index of Relative Importance. Avian species were the most frequent prey we found in the stomachs of red foxes from South Bay (61%), whereas small rodents were most frequent for red foxes from Monterey County (62%). Small rodents were the most frequent prey we found in feral cats (63%). Carbon and nitrogen isotopic signatures for foxes supported stomach content findings. However, isotope results indicated that cats received a majority of their energy from a source other than rodents and outside the natural system, which differed from the stomach content analysis. We demonstrated the utility of both stable isotope and stomach content analyses to establish a more complete understanding of predators' diets. This information aids natural resource managers in planning and evaluating future predator-removal programs and increases our understanding of the impacts of nonnative foxes and cats on native species.

  15. Pemangsaan Propagul Mangrove Rhizophora sp. Sebagai Bukti Teori Dominance-Predation (Predation of Mangrove Propagule, Rhizophora sp. as Evidence of Dominance-Predation Theory

    Directory of Open Access Journals (Sweden)

    Rudhi Pribadi

    2014-06-01

    Propagule predation on mangrove in some extent reduced its viability to grow into seedling. The predation could happened before (pre-dispersal or after (post-dispersal the propagule drop from the tree.The reasearch was conducted in Pasar Banggi, Rembang District, Central Java. The aim was to investigate the predation rate of Rhizophora mucronata Lamk., R. stylosa Griff. and R. apiculata Blume propagules pre-dispersal and post-dispersal. Firstly, preface experiment for find domination spesies in the location, Second, with applied descriptive-based survey sampling and field experiment methods. Than all propagules of five replication trees were harvested and checked for its condition on pre-dispersal step. The third, with post-dispersal study there were twenty propagules from each spesies and tied them with used nylon string and placed on the forest floor for 2 until 18 days and checked its condition every 2 days after placement. This study is also set for tested the Smith’s theory on propagule predation related to tree domination. Rhizophora stylosa propagule was  most predated before they fall (mean 61,06%, range 45,40-76,05%, followed by R. apiculata (mean 58,18%, range 47,41-68% and the lowest isR. mucronata with mean 11,88% (range 7,06-15,71%. After 18 days of experiment in the field R. stylosa propagule in R. stylosa–dominated area was the lowest predated (mean 46,67% compared to propagule in the area dominated by R. apiculata (63,33% and also in R. mucronata area (83,33 Predated R. mucronata propagule is the highest in the R. mucronata dominated area (mean 95% compared with R. apiculata dominated area (mean 55% and also in R. stylosa dominated area (45%. Pradated of R. apiculata propagule is the lowest in the domination area of R. apiculata (50% compared with R. stylosa area domination with (mean 70% also R. mucronata (73,33%. The result showed that the theory of dominance-predation can be proved only for R. stylosa and R. apiculata spesies, but not for R

  16. Predation Risk within Fishing Gear and Implications for South Australian Rock Lobster Fisheries

    Science.gov (United States)

    Briceño, Felipe; Linnane, Adrian Joseph; Quiroz, Juan Carlos; Gardner, Caleb; Pecl, Gretta Tatyana

    2015-01-01

    Depredation of southern rock lobster (Jasus edwardsii) within fishing gear by the Maori octopus (Pinnoctopus cordiformis) has economic and ecological impacts on valuable fisheries in South Australia. In addition, depredation rates can be highly variable resulting in uncertainties for the fishery. We examined how in-pot lobster predation was influenced by factors such as lobster size and sex, season, fishing zone, and catch rate. Using mixed modelling techniques, we found that in-pot predation risk increased with lobster size and was higher for male lobsters. In addition, the effect of catch rate of lobsters on predation risk by octopus differed among fishing zones. There was both a seasonal and a spatial component to octopus predation, with an increased risk within discrete fishing grounds in South Australia at certain times of the year. Information about predation within lobster gear can assist fishery management decision-making, potentially leading to significant reduction in economic losses to the fishery. PMID:26489035

  17. Predation Risk within Fishing Gear and Implications for South Australian Rock Lobster Fisheries.

    Directory of Open Access Journals (Sweden)

    Felipe Briceño

    Full Text Available Depredation of southern rock lobster (Jasus edwardsii within fishing gear by the Maori octopus (Pinnoctopus cordiformis has economic and ecological impacts on valuable fisheries in South Australia. In addition, depredation rates can be highly variable resulting in uncertainties for the fishery. We examined how in-pot lobster predation was influenced by factors such as lobster size and sex, season, fishing zone, and catch rate. Using mixed modelling techniques, we found that in-pot predation risk increased with lobster size and was higher for male lobsters. In addition, the effect of catch rate of lobsters on predation risk by octopus differed among fishing zones. There was both a seasonal and a spatial component to octopus predation, with an increased risk within discrete fishing grounds in South Australia at certain times of the year. Information about predation within lobster gear can assist fishery management decision-making, potentially leading to significant reduction in economic losses to the fishery.

  18. Clay Caterpillar Whodunit: A Customizable Method for Studying Predator-Prey Interactions in the Field

    Science.gov (United States)

    Curtis, Rachel; Klemens, Jeffrey A.; Agosta, Salvatore J.; Bartlow, Andrew W.; Wood, Steve; Carlson, Jason A.; Stratford, Jeffrey A.; Steele, Michael A.

    2013-01-01

    Predator-prey dynamics are an important concept in ecology, often serving as an introduction to the field of community ecology. However, these dynamics are difficult for students to observe directly. We describe a methodology that employs model caterpillars made of clay to estimate rates of predator attack on a prey species. This approach can be…

  19. Extinction in a generalized Lotka-Volterra predator-prey model

    Directory of Open Access Journals (Sweden)

    Azmy S. Ackleh

    2000-01-01

    Full Text Available In this paper we discuss the asymptotic behavior of a predator-prey model with distributed growth and mortality rates. We exhibit simple criteria on the parameters which guarantee that all subpopulations but one predator-prey pair are driven to extinction as t→∞. Finally, we present numerical simulations to illustrate the theoretical results.

  20. Bristol Bay, Alaska Subarea ESI: NESTS (Nest Points)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for nesting seabirds (alcids, pelagic birds), gulls, terns, diving birds, and raptors in the Bristol Bay...

  1. Predation by Red Foxes (Vulpes vulpes at an Outdoor Piggery

    Directory of Open Access Journals (Sweden)

    Patricia A. Fleming

    2016-10-01

    Full Text Available Outdoor pig operations are an alternative to intensive systems of raising pigs; however for the majority of outdoor pork producers, issues of biosecurity and predation control require significant management and (or capital investment. Identifying and quantifying predation risk in outdoor pork operations has rarely been done, but such data would be informative for these producers as part of their financial and logistical planning. We quantified potential impact of fox predation on piglets bred on an outdoor pork operation in south-western Australia. We used remote sensor cameras at select sites across the farm as well as above farrowing huts to record interactions between predators and pigs (sows and piglets. We also identified animal losses from breeding records, calculating weaning rate as a proportion of piglets born. Although only few piglets were recorded lost to fox predation (recorded by piggery staff as carcasses that are “chewed”, it is likely that foxes were contributing substantially to the 20% of piglets that were reported “missing”. Both sets of cameras recorded a high incidence of fox activity; foxes appeared on camera soon after staff left for the day, were observed tracking and taking live piglets (despite the presence of sows, and removed dead carcasses from in front of the cameras. Newly born and younger piglets appeared to be the most vulnerable, especially when they are born out in the paddock, but older piglets were also lost. A significant ( p = 0.001 effect of individual sow identification on the weaning rate, but no effect of sow age (parity, suggests that individual sow behavior towards predators influences predation risk for litters. We tracked the movement of piglet carcasses by foxes, and confirmed that foxes make use of patches of native vegetation for cover, although there was no effect of paddock, distance to vegetation, or position on the farm on weaning rate. Trials with non-toxic baits reveal high levels

  2. Selective attention in peacocks during predator detection.

    Science.gov (United States)

    Yorzinski, Jessica L; Platt, Michael L

    2014-05-01

    Predation can exert strong selective pressure on the evolution of behavioral and morphological traits in birds. Because predator avoidance is key to survival and birds rely heavily on visual perception, predation may have shaped avian visual systems as well. To address this question, we examined the role of visual attention in antipredator behavior in peacocks (Pavo cristatus). Peacocks were exposed to a model predator while their gaze was continuously recorded with a telemetric eye-tracker. We found that peacocks spent more time looking at and made more fixations on the predator compared to the same spatial location before the predator was revealed. The duration of fixations they directed toward conspecifics and environmental features decreased after the predator was revealed, indicating that the peacocks were rapidly scanning their environment with their eyes. Maximum eye movement amplitudes and amplitudes of consecutive saccades were similar before and after the predator was revealed. In cases where conspecifics detected the predator first, peacocks appeared to learn that danger was present by observing conspecifics' antipredator behavior. Peacocks were faster to detect the predator when they were fixating closer to the area where the predator would eventually appear. In addition, pupil size increased after predator exposure, consistent with increased physiological arousal. These findings demonstrate that peacocks selectively direct their attention toward predatory threats and suggest that predation has influenced the evolution of visual orienting systems.

  3. Relative effects of exophytic predation, endophytic predation, and intraspecific competition on a subcortical herbivore: consequences to the reproduction of Ips pini and Thanasimus dubius.

    Science.gov (United States)

    Aukema, Brian H; Raffa, Kenneth F

    2002-12-01

    We used a laboratory assay to partition the effects of predation and intraspecific competition on the establishment, mating success, and brood development of an endophytic herbivore. We selected a system in which the same predator feeds both exophytically and endophytically on the same prey, to evaluate the role of herbivore feeding guild on predator numerical and functional responses. The bark beetle, Ips pini (Coleoptera: Scolytidae) reproduces within the stems of conifers. Males establish mating chambers under the bark, produce aggregation pheromones, and are subsequently joined by females that construct ovipositional galleries. Thanasimus dubius (Coleoptera: Cleridae) adults prey on adults alighting on the bark surface. T. dubius females then oviposit at the bark beetles' entrance sites, and their larvae prey on developing bark beetle larvae within the tree. We imposed a controlled 3×3 factorial design of prey and predator adult densities on red pine logs. Both predation and competition decreased I. pini reproduction. However, the per capita effect of predation was greater than competition, with one adult T. dubius reducing herbivore reproduction by an equivalent amount as four to five competing males and their harems. Increased densities of adult T. dubius on the plant surface reduced the number of prey captured per predator. Total predation on adults and larvae was similar. However, adult T. dubius on the plant surface ate approximately 18-35 times more I. pini per day than did their endophytic larvae. Within the plant, cannibalism among T. dubius, low herbivore densities, limited feeding times, and presumably the complex gallery architecture of I. pini reduced the number of predator progeny. The progeny of I. pini showed even sex ratios in the absence of predators, but were female biased when predators were present. We quantified a relatively narrow set of predator and prey densities that can generate replacement rates greater than one for this predator

  4. Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

    Science.gov (United States)

    Esque, Todd C.; Nussear, Kenneth E.; Drake, K. Kristina; Walde, Andrew D.; Berry, Kristin H.; Averill-Murray, Roy C.; Woodman, A. Peter; Boarman, William I.; Medica, Phil A.; Mack, Jeremy S.; Heaton, Jill S.

    2010-01-01

    Understanding predator–prey relationships can be pivotal in the conservation of species. For 2 decades, desert tortoise Gopherus agassizii populations have declined, yet quantitative evidence regarding the causes of declines is scarce. In 2005, Ft. Irwin National Training Center, California, USA, implemented a translocation project including 2 yr of baseline monitoring of desert tortoises. Unusually high predation on tortoises was observed after translocation occurred. We conducted a retrospective analysis of predation and found that translocation did not affect the probability of predation: translocated, resident, and control tortoises all had similar levels of predation. However, predation rates were higher near human population concentrations, at lower elevation sites, and for smaller tortoises and females. Furthermore, high mortality rates were not limited to the National Training Center. In 2008, elevated mortality (as high as 43%) occurred throughout the listed range of the desert tortoise. Although no temporal prey base data are available for analysis from any of the study sites, we hypothesize that low population levels of typical coyote Canis latrans prey (i.e. jackrabbits Lepus californicus and other small animals) due to drought conditions influenced high predation rates in previous years. Predation may have been exacerbated in areas with high levels of subsidized predators. Many historical reports of increased predation, and our observation of a range-wide pattern, may indicate that high predation rates are more common than generally considered and may impact recovery of the desert tortoise throughout its range.

  5. Temporal variation in seed predation by insects in a population of Syagrus romanzoffiana (Arecaceae) in Santa Catarina Island, SC, Brazil.

    Science.gov (United States)

    da Silva, F R; Begnini, R M; Lopes, B C; Castellani, T T

    2012-02-01

    Insect seed predation may vary depending on seed production. The present study considers the hypothesis that the rates of seed predation tend to be smaller in years of higher fruit production. Thus, we monitored the production of fruits and predation of seeds of the palm Syagrus romanzoffiana over 2 years in the Atlantic Forest (Parque Municipal da Lagoa do Peri, Florianópolis, SC, Brazil), between July 2006 and June 2008. Plots of 0.25 m(2) were fitted under 20 mother plants and fruits were monthly collected for assessment of abundance and seed predation. There was variation in fruit production between the 2 years and among reproductive plants. Predation rates were high and occurred in the predispersal phase by the Curculionidae Revena rubiginosa Boheman, Anchylorhynchus aegrotus Fahraeus, and Anchylorhynchus variabilis Gyllenhal. Seed predation by these species of Anchylorhynchus is first registered in the present study. In average, about 60% of the seeds monthly produced in the population tend to escape insect predation in year of high or low production, becoming available for recruitment. The predation rate was not related to the amount of fruits produced per reproductive plant. Also, different than expected, there was a positive relation between the rates of seed predation and the total of fruits produced monthly on the plots. Thus, no evidence for the satiation of insect seed predators was found in this study with S. romanzoffiana.

  6. A Generalist Protist Predator Enables Coexistence in Multitrophic Predator-Prey Systems Containing a Phage and the Bacterial Predator Bdellovibrio

    Directory of Open Access Journals (Sweden)

    Julia Johnke

    2017-10-01

    Full Text Available Complex ecosystems harbor multiple predators and prey species whose direct and indirect interactions are under study. In particular, the combined effects of predator diversity and resource preference on prey removal are not known. To understand the effect of interspecies interactions, combinations of micro-predators—i.e., protists (generalists, predatory bacteria (semi-specialists, and phages (specialists—and bacterial prey were tracked over a 72-h period in miniature membrane bioreactors. While specialist predators alone drove their preferred prey to extinction, the inclusion of a generalist resulted in uniform losses among prey species. Most importantly, presence of a generalist predator enabled coexistence of all predators and prey. As the generalist predator also negatively affected the other predators, we suggest that resource partitioning between predators and the constant availability of resources for bacterial growth due to protist predation stabilizes the system and keeps its diversity high. The appearance of resistant prey strains and subsequent evolution of specialist predators unable to infect the ancestral prey implies that multitrophic communities are able to persist and stabilize themselves. Interestingly, the appearance of BALOs and phages unable to infect their prey was only observed for the BALO or phage in the absence of additional predators or prey species indicating that competition between predators might influence coevolutionary dynamics.

  7. TRAP-NESTING BEES AND WASPS (HYMENOPTERA, ACULEATA IN A SEMIDECIDUAL SEASONAL FOREST FRAGMENT, SOUTHERN BRAZIL

    Directory of Open Access Journals (Sweden)

    PRISCILA S. OLIVEIRA

    Full Text Available ABSTRACT Trap-nesting bee and wasp inventories are common in Brazil but many phytophysiognomies are still poorly studied. The main objective of this study is to survey trap-nesting bees and wasps in a Semidecidual Seasonal Forest fragment. Also, we test the differences on nesting between interior and edge transects. A sum of 1,500 trap nests was made with bamboo cane internodes and two consecutive years were monitored. In the first year 46 nests were occupied by Pachodynerus grandis (19 nests, Pachodynerus guadulpensis (19, Centris analis (two, and Centris tarsata, Megachile fiebrigi, Megachile guaranitica, Megachile susurrans, Trypoxylon sp and Zethus smithii with one nest each. No statistical differences were found between interior and edge transects for richness and occupation rate, but the species composition was different. In the second year 39 nests were occupied by four species, three previously recorded, C. analis (seven nests, P. guadulpensis and P. grandis (six nests each, plus Monobia angulosa with 15 nests. Parasitoids from four families and one cleptoparasite were recorded and the mortality rate was higher in bees than in wasps. These findings reinforce the notion that trap nests assemblages from different studies are not directly comparable for richness and composition.

  8. Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA

    Science.gov (United States)

    Many empirical studies have shown that forest-breeding songbirds, and neotropical migrants in particular, are found in lower abundance in small patches of forest in the Eastern United States compared to similar, but larger patches in the same region. A common hypothesis for the ...

  9. Predators and the public trust.

    Science.gov (United States)

    Treves, Adrian; Chapron, Guillaume; López-Bao, Jose V; Shoemaker, Chase; Goeckner, Apollonia R; Bruskotter, Jeremy T

    2017-02-01

    Many democratic governments recognize a duty to conserve environmental resources, including wild animals, as a public trust for current and future citizens. These public trust principles have informed two centuries of U.S.A. Supreme Court decisions and environmental laws worldwide. Nevertheless numerous populations of large-bodied, mammalian carnivores (predators) were eradicated in the 20th century. Environmental movements and strict legal protections have fostered predator recoveries across the U.S.A. and Europe since the 1970s. Now subnational jurisdictions are regaining management authority from central governments for their predator subpopulations. Will the history of local eradication repeat or will these jurisdictions adopt public trust thinking and their obligation to broad public interests over narrower ones? We review the role of public trust principles in the restoration and preservation of controversial species. In so doing we argue for the essential roles of scientists from many disciplines concerned with biological diversity and its conservation. We look beyond species endangerment to future generations' interests in sustainability, particularly non-consumptive uses. Although our conclusions apply to all wild organisms, we focus on predators because of the particular challenges they pose for government trustees, trust managers, and society. Gray wolves Canis lupus L. deserve particular attention, because detailed information and abundant policy debates across regions have exposed four important challenges for preserving predators in the face of interest group hostility. One challenge is uncertainty and varied interpretations about public trustees' responsibilities for wildlife, which have created a mosaic of policies across jurisdictions. We explore how such mosaics have merits and drawbacks for biodiversity. The other three challenges to conserving wildlife as public trust assets are illuminated by the biology of predators and the interacting

  10. Nested Cohort - R software package

    Science.gov (United States)

    NestedCohort is an R software package for fitting Kaplan-Meier and Cox Models to estimate standardized survival and attributable risks for studies where covariates of interest are observed on only a sample of the cohort.

  11. Pre-nesting and nesting behavior of the Swainson's warbler

    Science.gov (United States)

    Meanley, B.

    1969-01-01

    The Swainson?s Warbler is one of the least known of southern birds. Although fairly common in some parts of its summer range, observations of its breeding biology have been made by very few persons. The present study was conducted mostly at Macon, Georgia; Pendleton Ferry, Arkansas; and Dismal Swamp, Virginia....In central Georgia and east-central Arkansas, Swainson?s Warblers usually arrive on their territories during the first two weeks in April. Territories in several localities ranged in size from 0.3 to 4.8 acres. A color-marked Arkansas male occupied the same territory for at least four months. Hostile encounters between territorial male Swainson?s Warblers usually take place along the boundary of adjacent territories. Paired males were more aggressive than unpaired males. Toward the end of an encounter one of the two males would usually perform a display in which the wing and tail feathers were spread and the tail vibrated. Following boundary encounters males drifted back onto their territories and usually sang unbroken courses of songs for several minutes.....During pre-nesting at Macon, a mated pair spent the day mostly on the ground within 20 feet of each other, often foragin g 3 to 4 feet apart. What may have been a form of courtship display, in which the male flew from a perch down to the female and either pecked her rump or pounced on her, occurred about three times each hour throughout the day. During this period the male sang less than at other times during the breeding season.....First nests are usually built by the first week in May. Although other investigators reported finding nests of this species outside of the defended territory, all nests that I have found were within the territory. The large, bulky nest of this species usually is placed 2-6 feet above the ground. It is built by the female from materials gathered close to the nest site; and takes two or three days to complete.....Three and occasionally four white eggs are laid. The female

  12. Pupation Behavior and Predation on Drosophila suzukii (Diptera: Drosophilidae) Pupae in Maine Wild Blueberry Fields.

    Science.gov (United States)

    Ballman, Elissa S; Collins, Judith A; Drummond, Francis A

    2017-12-05

    Drosophila suzukii (Matsumura; Diptera: Drosophilidae) is an invasive vinegar fly and pest of soft fruits in North America, including wild blueberries (Vaccinium angustifolium Aiton) in Maine. Despite its presence in the continental United States for 9 yr, little is known about its natural enemy complex. Here we report the results of a 3-yr study designed to identify naturally-occurring predators in Maine's wild blueberry fields. Experiments were conducted to determine pupation site and pupation depth to understand D. suzukii's predation vulnerability. Predation rates in the field of fully-exposed, caged, and buried pupae were measured. Pitfall traps were deployed to identify the potential predator assemblage, and laboratory experiments were conducted to determine how many pupae were consumed by commonly occurring ground beetle species (Carabidae) and field crickets (Gryllus pennsylvanicus Burmeister). The most commonly collected predators were ants, ground beetles, harvestmen, and field crickets. Significantly more pupae were found to occur in the soil compared to blueberry fruit, with most pupae in the top 0.5 cm layer of soil. Pupal predation rates in the field were high, with higher rates of predation on exposed pupae compared to buried pupae. Laboratory studies revealed that ground beetles and field crickets are likely predators of D. suzukii pupae. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  13. Spatial heterogeneity in post-dispersal predation on Prunus and Uvularia seeds.

    Science.gov (United States)

    Webb, Sara L; Willson, Mary F

    1985-08-01

    We investigated effects of seed density, distance from parent, and habitat (woods, open field) on post-dispersal predation risk (chiefly by rodents) for seeds of Prunus virginiana (Rosaceae). Additional study of the habitat effect (woods, open field, treefall gap) was made with seeds of Prunus avium (Rosaceae) and Uvularia grandiflora (Liliaceae). Density of Prunus seeds (range 2-40 seeds/group) did not affect predation risk for individual seeds. Distance from parent plants did influence predation risk, which was greatest directly beneath parents. This distance effect primarily comprised a sharp drop in risk within 2 m of parents, a distance too small to generate a "spacing rule" for conspecifics.We found that habitat strongly influenced predation intensity. Rates of removal of Prunus seeds were higher in woods than in open fields, except when overall predation intensity was very low and no pattern could be discerned. Prunus seed removal rates were higher in closed woods than in treefall gaps. Consequently, a Prunus seed will more likely escape predation if dispersed to an open site. In contrast, Uvularia seed removal rates were higher in open fields than in woods but did not differ between closed woods and tree-fall gaps.Predation intensity was spatially patchy between and within experimental arrays, but was consistent over time at some specific points in space, possibly reflecting home ranges of seed predators.

  14. Evaluation of Caspian tern (Hydroprogne caspia) and snowy plover (Charadrius alexandrinus nivosus) nesting on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California—2016 Annual Report

    Science.gov (United States)

    Hartman, C. Alex; Ackerman, Joshua T.; Herzog, Mark P.; Strong, Cheryl; Trachtenbarg, David; Shore, Crystal A.

    2017-05-08

    Executive SummaryIn order to address the 2008/10 and Supplemental 2014 NOAA Fisheries Biological Opinion for operation of the Federal Columbia River Power System, the U.S. Army Corps of Engineers (USACE) and the Bureau of Reclamation (Reclamation) developed and have begun implementation of Caspian tern (Hydroprogne caspia) management plans. This implementation includes redistribution of the Caspian terns in the Columbia River estuary and the mid-Columbia River region to reduce predation on salmonids listed under the Endangered Species Act. Key elements of the plans include (1) reducing nesting habitat for Caspian terns in the Columbia River estuary and the mid-Columbia River region, and (2) creating or modifying nesting habitat at alternative sites within the Caspian tern breeding range. USACE and Reclamation developed Caspian tern nesting habitat at the U.S. Fish and Wildlife Service Don Edwards San Francisco Bay National Wildlife Refuge (DENWR), California, prior to the 2015 nesting season. Furthermore, to reduce or eliminate potential conflicts between nesting Caspian terns and threatened western snowy plovers (Charadrius alexandrinus nivosus), nesting habitat for snowy plovers also was developed. Seven recently constructed islands within two managed ponds (Ponds A16 and SF2) of DENWR were modified to provide habitat attractive to nesting Caspian terns (5 islands) and snowy plovers (2 islands). These 7 islands were a subset of 46 islands recently constructed in Ponds A16 and SF2 to provide waterbird nesting habitat as part of the South Bay Salt Pond (SBSP) Restoration Project.We used social attraction methods (decoys and electronic call systems) to attract Caspian terns and snowy plovers to these seven modified islands, and conducted surveys between March and September of 2015 and 2016 to evaluate nest numbers, nest density, and productivity. Results from the 2015 nesting season, the first year of the study, indicated that island modifications and social

  15. Hierarchically nested river landform sequences

    Science.gov (United States)

    Pasternack, G. B.; Weber, M. D.; Brown, R. A.; Baig, D.

    2017-12-01

    River corridors exhibit landforms nested within landforms repeatedly down spatial scales. In this study we developed, tested, and implemented a new way to create river classifications by mapping domains of fluvial processes with respect to the hierarchical organization of topographic complexity that drives fluvial dynamism. We tested this approach on flow convergence routing, a morphodynamic mechanism with different states depending on the structure of nondimensional topographic variability. Five nondimensional landform types with unique functionality (nozzle, wide bar, normal channel, constricted pool, and oversized) represent this process at any flow. When this typology is nested at base flow, bankfull, and floodprone scales it creates a system with up to 125 functional types. This shows how a single mechanism produces complex dynamism via nesting. Given the classification, we answered nine specific scientific questions to investigate the abundance, sequencing, and hierarchical nesting of these new landform types using a 35-km gravel/cobble river segment of the Yuba River in California. The nested structure of flow convergence routing landforms found in this study revealed that bankfull landforms are nested within specific floodprone valley landform types, and these types control bankfull morphodynamics during moderate to large floods. As a result, this study calls into question the prevailing theory that the bankfull channel of a gravel/cobble river is controlled by in-channel, bankfull, and/or small flood flows. Such flows are too small to initiate widespread sediment transport in a gravel/cobble river with topographic complexity.

  16. Subtle Gardeners: Inland Predators Enrich Local Topsoils and Enhance Plant Growth.

    Science.gov (United States)

    Fedriani, José M; Garrote, Pedro José; Delgado, María del Mar; Penteriani, Vincenzo

    2015-01-01

    Inland vertebrate predators could enrich of nutrients the local top soils in the area surrounding their nests and dens by depositing faeces, urine, and prey remains and, thus, alter the dynamics of plant populations. Surprisingly, and in contrast with convincing evidence from coastal habitats, whether and how this phenomenon occurs in inland habitats is largely uncertain even though these habitats represent a major fraction of the earth's surface. We investigated during two consecutive breeding seasons the potential enrichment of the top-soils associated with inland ground-nesting eagle owls Bubo bubo, as well as its possible consequences in the growth of two common annual grasses in southern Spain. Top-soils associated with owl nests differed strongly and significantly from control top-soils in chemical parameters, mainly fertility-related properties. Specifically, levels of available phosphorus, total nitrogen, organic matter, and available potassium were 49.1, 5.6, 3.1, and 2.7 times higher, respectively, in top-soils associated with owl nests as compared to control top-soils. Germination experiments in chambers indicated that nutrient enrichment by nesting owls enhanced seedling growth in both annual grasses (Phalaris canariensis and Avena sativa), with seedling size being 1.4-1.3 times higher in owl nest top-soils than in control top-soils. Our experimental study revealed that pervasive inland, predatory birds can profoundly enrich the topsoil around their nests and, thus, potentially enhance local vegetation growth. Because diverse inland vertebrate predators are widespread in most habitats they have a strong potential to enhance spatial heterogeneity, impinge on plant communities, and exert an overlooked effect on primary productivity worldwide.

  17. Subtle Gardeners: Inland Predators Enrich Local Topsoils and Enhance Plant Growth.

    Directory of Open Access Journals (Sweden)

    José M Fedriani

    Full Text Available Inland vertebrate predators could enrich of nutrients the local top soils in the area surrounding their nests and dens by depositing faeces, urine, and prey remains and, thus, alter the dynamics of plant populations. Surprisingly, and in contrast with convincing evidence from coastal habitats, whether and how this phenomenon occurs in inland habitats is largely uncertain even though these habitats represent a major fraction of the earth's surface. We investigated during two consecutive breeding seasons the potential enrichment of the top-soils associated with inland ground-nesting eagle owls Bubo bubo, as well as its possible consequences in the growth of two common annual grasses in southern Spain. Top-soils associated with owl nests differed strongly and significantly from control top-soils in chemical parameters, mainly fertility-related properties. Specifically, levels of available phosphorus, total nitrogen, organic matter, and available potassium were 49.1, 5.6, 3.1, and 2.7 times higher, respectively, in top-soils associated with owl nests as compared to control top-soils. Germination experiments in chambers indicated that nutrient enrichment by nesting owls enhanced seedling growth in both annual grasses (Phalaris canariensis and Avena sativa, with seedling size being 1.4-1.3 times higher in owl nest top-soils than in control top-soils. Our experimental study revealed that pervasive inland, predatory birds can profoundly enrich the topsoil around their nests and, thus, potentially enhance local vegetation growth. Because diverse inland vertebrate predators are widespread in most habitats they have a strong potential to enhance spatial heterogeneity, impinge on plant communities, and exert an overlooked effect on primary productivity worldwide.

  18. Risk from cattle trampling to nests of an endangered passerine evaluated using artificial nest experiments and simulations

    Directory of Open Access Journals (Sweden)

    Brian W. Rolek

    2016-06-01

    Full Text Available Grasslands are often grazed by cattle and many grassland birds nest on the ground, potentially exposing nests to trampling. We tested for trampling risk introduced by cattle to nests of endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus using experimentally paired grids of artificial nests (i.e., clay targets similar in size to nests of Florida Grasshopper Sparrows and counted the number of clay targets that were broken in paired grazed and ungrazed enclosures. Clay targets in grazed grids were trampled 3.9% more often than their respective ungrazed grids, and measurements of cattle presence or density were correlated with the number of broken clay targets, suggesting that excluding cattle during breeding is an important management recommendation for the Florida Grasshopper Sparrow. Trampling rates within grazed enclosures were spatially homogeneous with respect to cattle infrastructure such as supplemental feeding troughs and fences, and forests and stocking density were poor predictors of trampling rates when excluding ungrazed grids. We used population viability analysis to compare quasi-extinction rates, intrinsic growth rates, and median abundance in grazed and ungrazed Florida Grasshopper Sparrow aggregations to further understand the biological significance of management aimed at reducing trampling rates during the breeding season. Simulations indicated that trampling from grazing increased quasi-extinction rates by 41% while reducing intrinsic growth rates by 0.048, and reducing median abundance by an average of 214 singing males after 50 years. Management should avoid grazing enclosures occupied by Florida Grasshopper Sparrows during the nesting season to minimize trampling rates. Our methods that combine trampling experiments with population viability analysis provide a framework for testing effects from trampling on other grassland ground-nesting birds, and can directly inform conservation and management of the

  19. Estuarine predation on radiotagged wild and domesticated sea trout ( Salmo trutta L.) smolts

    DEFF Research Database (Denmark)

    Dieperink, C.; Pedersen, Stig; Pedersen, Michael Ingemann

    2001-01-01

    days after entering the sea, both wild and domesticated smolts suffered a severe daily predation rate (range 20-34%). The results support the hypothesis of a transient period immediately after exposure to full-strength sea water, where smolts experience an elevated risk of predation. A transient......Avian predation on emigrating wild and domesticated sea trout smolts was investigated in a fjord in the western Baltic Sea. In April 1997, 50 domesticated and 50 wild smolts were intraperitoneally tagged with radio-transmitters and released in a small coastal stream. Predation was recorded...... by signal interception in an estuarine breeding colony of cormorants and herons near the outlet of the stream. Of the 78 emigrating smolts, 51 (65%) were recorded as eaten. Predation rates were significantly higher among small than large smolts and significantly higher among domesticated smolts. The first 2...

  20. Defaunation of large mammals leads to an increase in seed predation in the Atlantic forests

    Directory of Open Access Journals (Sweden)

    Mauro Galetti

    2015-01-01

    Full Text Available Defaunation can trigger cascading events in natural communities and may have strong consequences for plant recruitment in tropical forests. Several species of large seed predators, such as deer and peccaries, are facing dramatic population collapse in tropical forests yet we do not have information about the consequences of these extinctions for seed predation. Using remote camera traps we tested if defaunated forests have a lower seed predation rate of a keystone palm (Euterpe edulis than pristine areas. Contrary to our expectation, we found that seed predation rates were 2.5 higher in defaunated forests and small rodents were responsible for most of the seeds eaten. Our results found that defaunation leads to changes in the seed predator communities with potential consequences for plant–animal interactions.

  1. Fish egg predation by Baltic sprat and herring: do species characteristics and development stage matter?

    DEFF Research Database (Denmark)

    Neumann, Viola; Köster, Fritz; Eero, Margit

    2017-01-01

    Predation of eggs by clupeids has been identified as a major factor contributing to early life stage mortality of Baltic cod. We used data from ichthyoplankton sampling and clupeid stomach analyses to investigate whether eggs of other fish species are to a similar extent subject to predation...... generally negatively selected by both predators, while fish eggs were non-selectively consumed in summer. Predation is suggested to account for a large fraction of mortality of cod eggs at older stages, i.e. those eggs, which have survived the often detrimentally low oxygen concentration in and below...... the permanent halocline. The consumption rates of sprat eggs at all development stages relative to production rates were considerably lower compared to cod, suggesting that egg predation is of lesser importance for sprat recruitment....

  2. Smelling out predators is innate in birds

    NARCIS (Netherlands)

    Amo, L.; Visser, M.E.; Van Oers, K.

    2011-01-01

    The role of olfaction for predation risk assessment remains barely explored in birds, although predator chemical cues could be useful in predator detection under low visibility conditions for many bird species. We examine whether Great Tits Parus major are able to use the odour of mustelids to

  3. Role of intraguild predation in aphidophagous guilds

    Czech Academy of Sciences Publication Activity Database

    Hemptinne, J. L.; Magro, A.; Saladin, C.; Dixon, Anthony F. G.

    2012-01-01

    Roč. 136, č. 3 (2012), s. 161-170 ISSN 0931-2048 Institutional support: RVO:67179843 Keywords : aphidophagous guilds * cost of intraguild predation * interspecific predation * intraguild predation * ladybird beetles * omnivory Subject RIV: EH - Ecology, Behaviour Impact factor: 1.560, year: 2012

  4. Direct identification of predator-prey dynamics in gyrokinetic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Sumire, E-mail: sumire.kobayashi@lpp.polytechnique.fr; Gürcan, Özgür D [Laboratoire de Physique des Plasmas, CNRS, Paris-Sud, Ecole Polytechnique, UMR7648, F-91128 Palaiseau (France); Diamond, Patrick H. [University of California, San Diego, La Jolla, California 92093-0319 (United States)

    2015-09-15

    The interaction between spontaneously formed zonal flows and small-scale turbulence in nonlinear gyrokinetic simulations is explored in a shearless closed field line geometry. It is found that when clear limit cycle oscillations prevail, the observed turbulent dynamics can be quantitatively captured by a simple Lotka-Volterra type predator-prey model. Fitting the time traces of full gyrokinetic simulations by such a reduced model allows extraction of the model coefficients. Scanning physical plasma parameters, such as collisionality and density gradient, it was observed that the effective growth rates of turbulence (i.e., the prey) remain roughly constant, in spite of the higher and varying level of primary mode linear growth rates. The effective growth rate that was extracted corresponds roughly to the zonal-flow-modified primary mode growth rate. It was also observed that the effective damping of zonal flows (i.e., the predator) in the parameter range, where clear predator-prey dynamics is observed, (i.e., near marginal stability) agrees with the collisional damping expected in these simulations. This implies that the Kelvin-Helmholtz-like instability may be negligible in this range. The results imply that when the tertiary instability plays a role, the dynamics becomes more complex than a simple Lotka-Volterra predator prey.

  5. Predator and prey perception in copepods due to hydromechanical signals

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Visser, Andre

    1999-01-01

    of the different components of the fluid disturbance. We use this model to argue that prey perception depends on the absolute magnitude of the fluid velocity generated by the moving prey, while predator perception depends on the magnitude of one or several of the components of the fluid velocity gradients...... (deformation rate, vorticity, acceleration) generated by the predator. On the assumption that hydrodynamic disturbances are perceived through the mechanical bending of sensory setae, we estimate the magnitude of the signal strength due to each of the fluid disturbance components. We then derive equations...... for reaction distances as a function of threshold signal strength and the size and velocity of the prey or predator. We provide a conceptual framework for quantifying threshold signal strengths and, hence, perception distances. The model is illustrated by several examples, and we demonstrate, for example, (1...

  6. Response of beach-nesting American Oystercatchers to off-road vehicles: An experimental approach reveals physiological nuances and decreased nest attendance

    Science.gov (United States)

    Felton, Shilo K.; Pollock, Kenneth H.; Simons, Theodore R.

    2018-01-01

    Shorebird populations face increasing challenges as rising sea levels and growing human populations constrain their breeding habitats. On recreational beaches, the nesting season often coincides with a season of high visitor use, increasing the potential for conflict, which may negatively influence beach-nesting shorebird species. We designed a field experiment to study the responses of nesting American Oystercatchers (Haematopus palliatus) to off-road passenger vehicles (ORVs) at Cape Hatteras and Cape Lookout National Seashores in North Carolina, USA. We used continuous video and heart rate recordings to assess changes in the behavior and physiology of incubating oystercatchers. We conducted driving experiments affecting 7 nesting pairs in 2014 and 19 nesting pairs in 2015, between April and July of each year. Experimental treatments were repeated throughout the incubation period for each nest. Although responses were highly variable within and among pairs, paired randomized permutation tests indicated that, overall, oystercatcher pairs spent a greater proportion of time with their heads up and exhibited slower heart rates during driving treatments. Pairs also left their nests more frequently and attended their nests for a lower proportion of time during driving treatments, although these responses diminished over time. Higher nest attendance and lower departure rates late in incubation may have reflected a stronger attachment to nests closer to hatching or habituation to the driving treatment, although individuals continued to exhibit physiological responses to passing vehicles throughout incubation. Beach-nesting birds may benefit from reduced vehicle traffic at their nesting sites, allowing parents to spend more time attending the nest and less time on defensive behaviors.

  7. Predation-related costs and benefits of conspecific attraction in songbirds--an agent-based approach.

    Science.gov (United States)

    Szymkowiak, Jakub; Kuczyński, Lechosław

    2015-01-01

    Songbirds that follow a conspecific attraction strategy in the habitat selection process prefer to settle in habitat patches already occupied by other individuals. This largely affects the patterns of their spatio-temporal distribution and leads to clustered breeding. Although making informed settlement decisions is expected to be beneficial for individuals, such territory clusters may potentially provide additional fitness benefits (e.g., through the dilution effect) or costs (e.g., possibly facilitating nest localization if predators respond functionally to prey distribution). Thus, we hypothesized that the fitness consequences of following a conspecific attraction strategy may largely depend on the composition of the predator community. We developed an agent-based model in which we simulated the settling behavior of birds that use a conspecific attraction strategy and breed in a multi-predator landscape with predators that exhibited different foraging strategies. Moreover, we investigated whether Bayesian updating of prior settlement decisions according to the perceived predation risk may improve the fitness of birds that rely on conspecific cues. Our results provide evidence that the fitness consequences of conspecific attraction are predation-related. We found that in landscapes dominated by predators able to respond functionally to prey distribution, clustered breeding led to fitness costs. However, this cost could be reduced if birds performed Bayesian updating of prior settlement decisions and perceived nesting with too many neighbors as a threat. Our results did not support the hypothesis that in landscapes dominated by incidental predators, clustered breeding as a byproduct of conspecific attraction provides fitness benefits through the dilution effect. We suggest that this may be due to the spatial scale of songbirds' aggregative behavior. In general, we provide evidence that when considering the fitness consequences of conspecific attraction for

  8. Predation-Related Costs and Benefits of Conspecific Attraction in Songbirds—An Agent-Based Approach

    Science.gov (United States)

    Szymkowiak, Jakub; Kuczyński, Lechosław

    2015-01-01

    Songbirds that follow a conspecific attraction strategy in the habitat selection process prefer to settle in habitat patches already occupied by other individuals. This largely affects the patterns of their spatio-temporal distribution and leads to clustered breeding. Although making informed settlement decisions is expected to be beneficial for individuals, such territory clusters may potentially provide additional fitness benefits (e.g., through the dilution effect) or costs (e.g., possibly facilitating nest localization if predators respond functionally to prey distribution). Thus, we hypothesized that the fitness consequences of following a conspecific attraction strategy may largely depend on the composition of the predator community. We developed an agent-based model in which we simulated the settling behavior of birds that use a conspecific attraction strategy and breed in a multi-predator landscape with predators that exhibited different foraging strategies. Moreover, we investigated whether Bayesian updating of prior settlement decisions according to the perceived predation risk may improve the fitness of birds that rely on conspecific cues. Our results provide evidence that the fitness consequences of conspecific attraction are predation-related. We found that in landscapes dominated by predators able to respond functionally to prey distribution, clustered breeding led to fitness costs. However, this cost could be reduced if birds performed Bayesian updating of prior settlement decisions and perceived nesting with too many neighbors as a threat. Our results did not support the hypothesis that in landscapes dominated by incidental predators, clustered breeding as a byproduct of conspecific attraction provides fitness benefits through the dilution effect. We suggest that this may be due to the spatial scale of songbirds’ aggregative behavior. In general, we provide evidence that when considering the fitness consequences of conspecific attraction for

  9. Predation-related costs and benefits of conspecific attraction in songbirds--an agent-based approach.

    Directory of Open Access Journals (Sweden)

    Jakub Szymkowiak

    Full Text Available Songbirds that follow a conspecific attraction strategy in the habitat selection process prefer to settle in habitat patches already occupied by other individuals. This largely affects the patterns of their spatio-temporal distribution and leads to clustered breeding. Although making informed settlement decisions is expected to be beneficial for individuals, such territory clusters may potentially provide additional fitness benefits (e.g., through the dilution effect or costs (e.g., possibly facilitating nest localization if predators respond functionally to prey distribution. Thus, we hypothesized that the fitness consequences of following a conspecific attraction strategy may largely depend on the composition of the predator community. We developed an agent-based model in which we simulated the settling behavior of birds that use a conspecific attraction strategy and breed in a multi-predator landscape with predators that exhibited different foraging strategies. Moreover, we investigated whether Bayesian updating of prior settlement decisions according to the perceived predation risk may improve the fitness of birds that rely on conspecific cues. Our results provide evidence that the fitness consequences of conspecific attraction are predation-related. We found that in landscapes dominated by predators able to respond functionally to prey distribution, clustered breeding led to fitness costs. However, this cost could be reduced if birds performed Bayesian updating of prior settlement decisions and perceived nesting with too many neighbors as a threat. Our results did not support the hypothesis that in landscapes dominated by incidental predators, clustered breeding as a byproduct of conspecific attraction provides fitness benefits through the dilution effect. We suggest that this may be due to the spatial scale of songbirds' aggregative behavior. In general, we provide evidence that when considering the fitness consequences of conspecific

  10. Learned predation risk management by spider mites

    Directory of Open Access Journals (Sweden)

    Thomas eHackl

    2014-09-01

    Full Text Available Predation is a prime selective force shaping prey behavior. Investment in anti-predator behavior is traded-off against time and energy for other fitness-enhancing activities such as foraging or reproduction. To optimize this benefit/cost trade-off, prey should be able to innately and/or by experience modulate their behavior to the level of predation risk. Here, we assessed learned predation risk management in the herbivorous two-spotted spider mite Tetranychus urticae. We exposed spider mites coming from benign (naïve or high immediate predation risk (experienced environments to latent and/or no risk and assessed their site choice, activity and oviposition. Benign environments were characterized by the absence of any predator cues, high immediate risk environments by killed spider mites, physical presence of the predatory mite Phytoseiulus persimilis and associated chemosensory traces left on the surface, and latent risk environments by only predator traces. In the no-choice experiment both naïve and experienced spider mites laid their first egg later on leaves with than without predator traces. Irrespective of predator traces presence/absence, experienced mites laid their first egg earlier than naïve ones did. Naïve spider mites were more active, indicating higher restlessness, and laid fewer eggs on leaves with predator traces, whereas experienced mites were less active and laid similar numbers of eggs on leaves with and without predator traces. In the choice experiment both naïve and experienced spider mites preferentially resided and oviposited on leaves without predator traces but experienced mites were less active than naïve ones. Overall, our study suggests that spider mites experienced with high predation risk behave bolder under latent risk than naïve spider mites. Since predator traces alone do not indicate immediate risk, we argue that the attenuated anti-predator response of experienced spider mites represents adaptive learned

  11. Home range utilisation and long-range movement of estuarine crocodiles during the breeding and nesting season.

    Directory of Open Access Journals (Sweden)

    Hamish A Campbell

    Full Text Available The estuarine crocodile (Crocodylus porosus is the apex-predator in waterways and coastlines throughout south-east Asia and Australasia. C. porosus pose a potential risk to humans, and management strategies are implemented to control their movement and distribution. Here we used GPS-based telemetry to accurately record geographical location of adult C. porosus during the breeding and nesting season. The purpose of the study was to assess how C. porosus movement and distribution may be influenced by localised social conditions. During breeding, the females (2.92 ± 0.013 metres total length (TL, mean ± S.E., n = 4 occupied an area<1 km length of river, but to nest they travelled up to 54 km away from the breeding area. All tagged male C. porosus sustained high rates of movement (6.49 ± 0.9 km d(-1; n = 8 during the breeding and nesting period. The orientation of the daily movements differed between individuals revealing two discontinuous behavioural strategies. Five tagged male C. porosus (4.17 ± 0.14 m TL exhibited a 'site-fidelic' strategy and moved within well-defined zones around the female home range areas. In contrast, three males (3.81 ± 0.08 m TL exhibited 'nomadic' behaviour where they travelled continually throughout hundreds of kilometres of waterway. We argue that the 'site-fidelic' males patrolled territories around the female home ranges to maximise reproductive success, whilst the 'nomadic' males were subordinate animals that were forced to range over a far greater area in search of unguarded females. We conclude that C. porosus are highly mobile animals existing within a complex social system, and mate/con-specific interactions are likely to have a profound effect upon population density and distribution, and an individual's travel potential. We recommend that impacts on socio-spatial behaviour are considered prior to the implementation of management interventions.

  12. Contrasting nest survival patterns for ducks and songbirds in northern mixed-grass prairie

    Science.gov (United States)

    Grant, Todd; Shaffer, Terry L.; Madden, Elizabeth M.; Nenneman, Melvin P.

    2017-01-01

    Management actions intended to protect or improve habitat for ducks may benefit grassland-nesting passerines, but scant information is available to explore this assumption. During 1998–2003, we examined nest survival of ducks and songbirds to determine whether effects of prescribed fire and other habitat features (e.g., shrub cover and distance to habitat edges) were similar for ducks and passerines breeding in North Dakota. We used the logistic-exposure method to estimate survival of duck and songbird nests (n = 3,171). We used an information-theoretic approach to identify factors that most influenced nest survival. Patterns of nest survival were markedly different between taxonomic groups. For ducks, nest survival was greater during the first postfire nesting season (daily survival rate [DSR] = 0.957, 85% CI = 0.951–0.963), relative to later postfire nesting seasons (DSR = 0.946, 85% CI = 0.942–0.950). Furthermore duck nest survival and nest densities were inversely related. Duck nest survival also was greater as shrub cover decreased and as distance from cropland and wetland edges increased. Passerines had lower nest survival during the first postfire nesting season (DSR = 0.934, 85% CI = 0.924–0.944), when densities also were low compared to subsequent postfire nesting seasons (DSR = 0.947, 85% CI = 0.944–0.950). Parasitism by brown-headed cowbirds (Molothrus ater) reduced passerine nest survival and this effect was more pronounced during the first postfire nesting season compared to subsequent nesting seasons. Passerine nest survival was greater as shrub cover decreased and perhaps for more concealed nests. Duck and songbird nest survival rates were not correlated during this study and for associated studies that examined additional variables using the same dataset, suggesting that different mechanisms influenced their survival. Based on our results, ducks should not be considered direct surrogates for passerines

  13. Interspecific nest use by aridland birds

    Science.gov (United States)

    Deborah M. Finch

    1982-01-01

    Nest holes drilled by woodpeckers (Picidae) are frequently used by secondary cavity-nesting species, but interspecific use of open and domed nests is less well known. Nests constructed by many southwestern desert birds last longer than one year (pers. obs.) and are consequently reused by the same pair (e.g., Abert's Towhees [Pipilo aberti], pers. obs.) or by other...

  14. Constructing bald eagle nests with natural materials

    Science.gov (United States)

    T. G. Grubb

    1995-01-01

    A technique for using natural materials to build artificial nests for bald eagles (Haliaeetus leucocephalus) and other raptors is detailed. Properly constructed nests are as permanently secured to the nest tree or cliff substrate as any eagle-built nest or human-made platform. Construction normally requires about three hours and at least two people. This technique is...

  15. Nest use is influenced by the positions of nests and drinkers in aviaries.

    Science.gov (United States)

    Lentfer, T L; Gebhardt-Henrich, S G; Fröhlich, E K F; von Borell, E

    2013-06-01

    The influence of the nest location and the placement of nipple drinkers on