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To avoid potentially noxious prey, predators need to discriminate between palatable and unpalatable prey species. Unpalatable prey often exhibits visual warning signals, which can consist of multiple components, such as color and pattern. Although the role of particular components of visual warning signals in predator discrimination learning has been intensively studied, the importance of different components for predator memory is considerably less understood. In this study, we tested adult wild-caught great tits (Parus major) to find out, which components of prey visual warning signals are important when the birds learn to discriminate between palatable and unpalatable prey, and when they remember their experience over a longer time period. Birds were trained to discriminate between palatable and unpalatable artificial prey items that differed in both color and pattern. After 4 wk, the birds were retested in 3 groups: the first group was presented with the same prey as in the training, the second group was tested with the two prey types differing only in color, and the third group could use only the pattern as a discrimination trait. The results suggest that the birds remember their experience with unpalatable prey even after the period of 4 wk. Although the color appears to be more important than the pattern, the combination of both signal components is more effective for prey recognition after several weeks than either the color or pattern alone. [ABSTRACT FROM AUTHOR]

The New Zealand fairy tern/tara iti (Sternula nereis davisae; NZFT) is New Zealand's most endangered bird, with approximately 40 individuals remaining. Due to previous poor breeding success, this species is on the brink of extinction. Nest failures occur because of adverse weather, predation, and potentially nest disturbance. We observed parental behaviour of 11 nesting pairs from November 2020 to January 2021 at three sites: Mangawhai, Waipu and Pakiri. Overall, avian predator disturbance was low at all nests, and most disturbance events were by interactions between conspecifics. Responses to conspecific disturbances were lowest for the three closely nesting pairs and highest for the three solitary nests. We measured the frequency of chick feeding and found feeding rates varied considerably between nests. Defensive response rates and feeding rates varied between nests but we found no relationship between the proportion of responses to disturbance and feeding rates. We found no relationship between feeding rate and tidal state. This could be due to our small sample size and the duration of our observation period (30 min). We urge future researchers to increase observation period time. With an understanding of feeding rates and disturbance, informed decisions can be made to support the conservation of NZFT. [ABSTRACT FROM AUTHOR]

Investigations of seasonal variations in nest predation rates yield highly variable results. Some investigations argue that search image is responsible for some of the nest-predation patterns, but as far as we know, this study is the first in which search image in connection with seasonal variation in nest-predation rate has been experimentally tested. We used 1457 artificial nests placed in an identical way during the months of March to August, either in the two months consecutively or early and late within one of the two months, between the years 2000 and 2023. In addition, we compared the change in nest-predation rates at 113 artificial and 460 natural nests between the same two months. We estimated the seasonal variation in the abundance of breeding birds in the study area with 140 point counts to find the abundance of different species at the times when they normally breed. We found a strong and consistent seasonal variation in the nest-predation rate, with the highest predation rate in the middle of the breeding season. There was a similar change in the predation rate on natural and artificial nests between May and June. From July to August, the predation rate on artificial nests decreased significantly, while the search-image experiment revealed a significant increase between the same two months. A generalized linear mixed-effect model analysis found that the variation in nest-predation rates on artificial nests was significantly affected by seasonal variation in the estimated number of natural nests, that nests in trees were predated more often than nests on the ground, and that nests in the open landscape and on forest edges suffered higher predation rates than nests inside a forest. Mammals were nest predators significantly more often inside forests and on forest edges than in the open landscape, but birds were much more common nest predators than mammals independent of placement and habitat. Our experiment shows that search image explains the seasonal variation in nest-predation rates. However, more investigations are needed to find the reasons for the variation in published results on seasonal variation. Further, experimental testing on search image to find its contribution to the seasonal variation in nest-predation rates in other areas is also needed. [ABSTRACT FROM AUTHOR]

The camouflage of crab spiders on flowers have been extensively studied, primarily focusing on species with uniform coloration. In reality, more than 50 flower-visiting spider species from seven families do not possess uniform coloration. However, there is a lack of exploration regarding them, leaving their cryptic nature uncertain. Additionally, little is known about the flower-visiting strategies employed by spiders at different developmental stages. To address these issues, we investigated Ebrechtella tricuspidata, a crab spider species exhibiting distinct abdomen and carapace colors. Notably, during our earlier field survey, we found that the juvenile spiders appeared on chamomile flowers (Matricaria recutita) significantly more frequently compared to the females. Our visual modeling showed that the spider's carapace on flower petals was detectable, whereas the abdomen matched the flower petals in both chromatic and achromatic contrast, making it unlikely to be detected by avian. Our predation experiment revealed that the probability of being detected and attacked was significantly lower for spiders on flower petals. Moreover, the attacked percentage of juveniles on petals was significantly lower than that of females. Combined with our previous field findings, we predict that spiders in different developmental stages may employ different flower-visiting strategies according to their predation risk. Overall, our study demonstrated that imperfect crypsis of E. tricuspidata on flower prevents avian predation effectively, and the higher presence of juvenile spiders on flowers may be attributed to their lower predation risk. Significance statement: Crab spiders are renowned sit-and-wait predators and provide an ideal model for studying animal camouflage. It is widely acknowledged that these spiders exploit flowers of matching hues to deceive their prey. However, there is a pressing need for broader investigations encompassing the camouflage of crab spiders with non-uniform body colors to predators and their flower visiting strategies during ontogeny. To investigate these questions, we conducted avian visual modeling and behavioral experiments. Our findings demonstrated that distinct local body part did not significantly impact overall concealment, suggesting that camouflage is prevalent not only among flower-visiting spiders sporting uniform coloration but also among those with different colored abdomen and carapace. Furthermore, juvenile spiders on flower experienced lower predation risk than females, indicating that spiders at different stages face distinct levels of predation risk. Combined with our previous field findings that juvenile spiders were significantly more commonly found on flowers than females, we predict that spiders may employ varied flower-visiting strategies throughout their developmental stages, where the increasing predation risk leads to a decreased presence of spiders on flowers as they mature during ontogeny. [ABSTRACT FROM AUTHOR]

Dedicated conservation efforts spanning the past two decades have saved the Fennoscandian Arctic fox (Vulpes lagopus) population from local extinction, and extensive resources continue to be invested in the species' conservation and management. Although increasing, populations remain isolated, small and are not yet viable in the longer term. An understanding of causes of mortality are consequently important to optimize ongoing conservation actions. Golden eagles (Aquila chrysaetos) are a predator of Arctic foxes, yet little information on this interaction is available in the literature. We document and detail six confirmed cases of Golden eagle depredation of Arctic foxes at the Norwegian captive breeding facility (2019–2022), where foxes are housed in large open‐air enclosures in the species' natural habitat. Here, timely detection of missing/dead foxes was challenging, and new insights have been gained following recently improved enclosure monitoring. Golden eagle predation peaked during the winter months, with no cases reported from June to November. This finding contrasts with that which is reported from the field, both for Arctic and other fox species, where eagle depredation peaked at dens with young (summer). While the seasonality of depredation may be ecosystem specific, documented cases from the field may be biased by higher survey efforts associated with the monitoring of reproductive success during the summer. Both white and blue color morphs were housed at the breeding station, yet only white foxes were preyed upon, and mortality was male biased. Mitigation measures and their effectiveness implemented at the facility are presented. Findings are discussed in the broader Arctic fox population ecology and conservation context. [ABSTRACT FROM AUTHOR]

Camouflage is often considered a daytime phenomenon based on light and shade. Nocturnal camouflage can also occur, but its mechanistic basis remains unclear. Here, we analyze the conditions for background matching (BM) of avian predators against the night sky. Such concealment is achieved when the contrast between the predator and the sky is smaller than the contrast detection threshold of prey. This condition cannot be fulfilled under isotropic skies, as in fully overcast or moonless nights. However, on clear moonlit nights, the isotropy of the sky radiance is broken due to the presence of the Moon, and the conditions for BM can be met for a wide range of sky directions. This effect is mainly dependent on the altitude of the Moon above the horizon, rather than on Moon phase. We have modeled the feasibility of concealment through BM of a typically white barn owl ( Tyto alba ) when hunting rodents, based on its contrast against the moonlit sky. We considered the radiometric quantities of the sky, the ground, and the bird's undersides. Our results show that a barn owl with highly reflecting underparts may approach a rodent from broad regions of the moonlit sky while keeping itself below the contrast detection threshold of the mouse M-cones and rods. S-cones, in turn, remain below their excitation threshold for most of the lunar cycle. Our results demonstrate that the white color of barn owls serves as camouflage tailored to the moonlit sky background, providing a mechanistic basis for understanding nocturnal camouflage., Competing Interests: Competing interests statement:The authors declare no competing interest.

When different introduced species across trophic levels (parasite, predator) invade island systems, they may pose significant threats to nesting birds. In this study, we measure nesting height and infer causes of offspring mortality in the critically endangered Medium Tree Finch (Camarhynchus pauper), an island endemic restricted to Floreana Island on the Galápagos Archipelago. Considering all nests at which a male built a nest, sang and attempted to attract a female (n = 222 nests), only 10.4% of nests produced fledglings (5% of nests had total fledging success, 5.4% of nests had partial fledging success). Of the 123 nests chosen by a female, 18.7% produced fledglings and of 337 eggs laid, 13.4% produced fledglings. Pairing success was higher for older males, but male age did not predict nesting success. All nests with chicks were infested with avian vampire fly larvae (Philornis downsi). We attributed the cause of death to avian vampire fly if chicks were found dead in the nest with fly larvae or pupae (45%) present. We inferred avian (either Asio flammeus galapagoensis or Crotophaga ani) predation (24%) if the nest was empty but dishevelled; and black rat (Rattus rattus) predation (20%) if the nest was empty but undamaged. According to these criteria, the highest nests were depredated by avian predators, the lowest nests by rats, and intermediate nests failed because of avian vampire fly larvae. In conclusion, there is no safe nesting height on Floreana Island under current conditions of threats from two trophic levels (introduced parasitic dipteran, introduced mammalian/avian predators; with Galápagos Short-Eared Owls being the only native predator in the system).

When different introduced species across trophic levels (parasite, predator) invade island systems, they may pose significant threats to nesting birds. In this study, we measure nesting height and infer causes of offspring mortality in the critically endangered Medium Tree Finch (Camarhynchus pauper), an island endemic restricted to Floreana Island on the Galápagos Archipelago. Considering all nests at which a male built a nest, sang and attempted to attract a female (n = 222 nests), only 10.4% of nests produced fledglings (5% of nests had total fledging success, 5.4% of nests had partial fledging success). Of the 123 nests chosen by a female, 18.7% produced fledglings and of 337 eggs laid, 13.4% produced fledglings. Pairing success was higher for older males, but male age did not predict nesting success. All nests with chicks were infested with avian vampire fly larvae (Philornis downsi). We attributed the cause of death to avian vampire fly if chicks were found dead in the nest with fly larvae or pupae (45%) present. We inferred avian (either Asio flammeus galapagoensis or Crotophaga ani) predation (24%) if the nest was empty but dishevelled; and black rat (Rattus rattus) predation (20%) if the nest was empty but undamaged. According to these criteria, the highest nests were depredated by avian predators, the lowest nests by rats, and intermediate nests failed because of avian vampire fly larvae. In conclusion, there is no safe nesting height on Floreana Island under current conditions of threats from two trophic levels (introduced parasitic dipteran, introduced mammalian/avian predators; with Galápagos Short-Eared Owls being the only native predator in the system). [ABSTRACT FROM AUTHOR]

Globally, human-caused environmental impacts, such as habitat loss, have seriously impacted raptor species, with some 50% of species having decreasing populations. We analyzed global patterns of distribution of all 557 raptor species, focusing on richness, endemism, geographic range, conservation status, and population trends. Highest species diversity, endemism, species at risk, or restricted species were concentrated in different regions. Patterns of species distribution greatly differed between nocturnal and diurnal species. To test the efficiency of the global protected areas in conserving raptors, we simulated and compared global reserve systems created with strategies aiming at: 1) constraining the existing system into the final solution; and 2) minimizing the socioeconomic cost of reserve selection. We analyzed three targets of species distribution to be protected (10, 20, 30%). The first strategy was more efficient in meeting targets and less efficient in cost and compactness of reserves. Focusing on actions in the existing protected areas is fundamental to consolidate conservation, and politically and economically more viable than creating new reserves. However, creating new reserves is essential to protect more populations throughout the species' geographic range. Our findings provide a fundamental understanding of reserves to maintain raptor diversity and reduce the global population and species extinction crisis. [ABSTRACT FROM AUTHOR]

Abstract The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top‐down control of herbivorous insects.

Disturbance from human activity can cause reduced productivity of coastal birds that nest on sandy beaches. A common method to protect coastal birds from human disturbance is the use of signs and fencing to close off a section of beach used for breeding. This management action requires public compliance and might require enforcement, such as in the use of volunteer stewards stationed at protected colonies that provide education and enforcement. I assessed the effectiveness of active stewardship as a conservation measure to protect nesting Least Terns (Sternula antillarum) in coastal Mississippi by determining if colony-level productivity (fledglings produced per nest) was correlated with stewardship effort (hours that stewards protected each colony), the rate of disturbance from human and natural sources, and additional factors. Observers surveyed 24 Least Tern colonies in Harrison County, Mississippi, twice weekly during the 2017–2019 breeding seasons to record the number of nests present, the fate of marked nests, predator tracks within the colony, and the number of fledglings produced per colony. Concurrently, during their work shifts, stewards recorded all sources and durations of disturbance events that caused the terns to flush or respond with defense. Least Tern daily nest survival increased with colony size and stewardship effort, and was lower during intervals that included weekends and evidence of owl presence. Total productivity was negatively associated with avian predator disturbance rate and the total time adults spent flushed, but was not associated with stewardship effort. The results of this study demonstrate that active stewardship can have a positive effect on Least Tern productivity by increasing nest success, whereas current stewardship practices were not sufficient to increase chick survival, even in a system with a paucity of ground predators. LAY SUMMARY Birds that nest on public sandy beaches benefit from protective fencing and educational signs, but additional benefits may occur if volunteer stewards are stationed at the protected area. I assessed whether the presence of stewards benefited nesting Least Terns by reducing human disturbance and increasing reproductive success at breeding colonies. Audubon Mississippi staff monitored Least Tern colonies in coastal Mississippi from 2017 to 2019 while seasonal stewards observed the extent of disturbance at each colony. Colonies with greater disturbance rates were less productive, and stewardship efforts benefited colonies by increasing nest hatch probability. Posting stewards at breeding colonies is an effective management strategy for conserving Least Terns, although additional management actions are likely needed to increase chick survival. [ABSTRACT FROM AUTHOR]

Prey detection and selection by birds can be influenced by prey coloration. Whereas certain colours can indicate to predators the unpalatability of prey (i.e. aposematism), other colours can render prey cryptic against the background. However, there are discrepancies in the response of birds to prey coloration reported in different studies. Such discrepancies can be the result of geographical or temporal (e.g. seasonal) differences between studies if birds in different regions respond differently to coloration or if responses vary seasonally due to changes in bird composition. Experimental studies aiming to understand bird responses to prey colour should consider the effect of geographical variation while accounting for seasonal as well as interannual variability. We investigated the effects of colour on attack rates by exposing plasticine caterpillars of different colours to bird communities in 13 Mediterranean forests in central Spain for a period from 17 weeks to 7 months. Overall, yellow and green dummy caterpillars suffered the lowest attack rates. We also observed a bimodal pattern of bird attack rates through time, with highest predation occurring in late winter and summer (June to September). Low attack rates on yellow dummies are probably a consequence of aposematism, while low attack rates on green dummies probably resulted from crypsis. Rapid decreases in attack rates over time are probably a result of avoidance learning, whereas the increase in attacks in summer could be explained by the increase in fledglings and migrant birds. • Yellow dummy caterpillars received fewer bird attacks, probably due to aposematism. • Green caterpillars received fewer bird attacks, probably due to reduced detectability. • Birds predominantly attacked caterpillars with dark colours. • The effect of dummy prey colour on bird predation was consistent across sites. • Predation rate varied over time, with maximum rates in the warmest months. [ABSTRACT FROM AUTHOR]

The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top‐down control of herbivorous insects. [ABSTRACT FROM AUTHOR]

Males of the green June beetle Cotinis nitida are regularly attacked by birds as they search for females on lawns but which bird species feeds on the beetle changes from year to year. In 2018 for the first time on a farm in northern Virginia, brown thrashers (Toxostomum rufum) joined blue jays (Cyanocitta cristata) as major predators of the beetles. The two species employed very different tactics when hunting for June beetles, with the thrashers searching while walking forward on the mowed lawn while the jays scanned for beetles when perched in trees about the lawn. The beetles became very scarce at the lawn in early July in 2017 and 2018 and their predators apparently moved elsewhere. Subsequently, male beetles were occasionally observed patrolling a nearby hayfield in search of mates with rare copulations recorded after July 15. Because predatory birds could not exploit the beetles in the tall grass of the hayfield it seems likely that the mowed lawn constituted an evolutionarily novel ecological trap which made searching beetles conspicuous and easily captured by beetle-hunting birds. [ABSTRACT FROM AUTHOR]

Nest predation is the most important factor causing reproductive failure in open-cup nesting birds. Therefore, it represents a strong selection agent shaping reproductive strategies. To understand how predation affects avian populations, it is crucial to understand how predation effects on nesting success vary in space and time, and which ecological factors determine variation in predation rates. Artificial nests are commonly used to evaluate nest predation rates, but their use is criticised for not providing predation rates comparable with natural nests, either because timing of predation or predator species targeting the nests differ. However, use of artificial nests allows us to standardize nest characteristics between sites and across time, even outside the breeding season of most birds. Here, we present data on 576 artificial nests gathered over several years that explore how nest predation rates vary over the year. We found that predation rates on artificial nests show seasonal variation where rates are high during the bird breeding season and low outside the breeding season. Avian and mammalian predators tend to display different nest predation behaviours. The frequency of predation events by avian predators follows a similar seasonal pattern as predation rates, whereas mammalian predators show elevated, but stable, frequency of predation events across the breeding season. Our study supports the commonly reported temporal variation in nest predation rates, indicating that avian predators actively search for bird nests as food during the bird breeding season, while mammalian predators seem to prey on bird nests incidentally. [ABSTRACT FROM AUTHOR]

We review entomological aspects of the rearing of muga silkworms (Antheraea assamensis) and eri silkworms (Samia ricini) from egg to adult in northeast India with the aim of harvesting cocoons for silk. Rearing of the latter species, ericulture, is also practiced to provide pupae for human consumption among tribal peoples in rural villages. Muga silkworms are reared outdoors and are subject to a large number of biotic and abiotic challenges such as parasitoids and predators, resulting in major losses of the crop. Eri silkworms are reared indoors and suffer far fewer losses. Based on our recent observations and early literature, many of the practices we observed in these two forms of sericulture have not changed in more than two hundred years. The notion of peace silk (silk production without killing the pupae) is discredited, but we conclude that the production of eri silk is environmentally friendly. [ABSTRACT FROM AUTHOR]

Shallow freshwater aquatic ecosystems are discrete feeding patches for fish eating birds. A unique feature of these ecosystems is that their physical conditions can change dramatically in a short period of time, particularly temperature, turbidity, and dissolved oxygen. Based on previous research we predicted that increasing turbidity will reduce the availability of fish to birds due to reduced visibility, while increasing temperature and decreasing dissolved oxygen will increase their availability through increases in activity and movement towards the more oxygenated surface areas, respectively. We also predicted that overall abundance of fish should increase feeding activity by terns.We measured these environmental variables, bird activity, and fish abundance from May to August from 2006 to 2008 in a marsh in southern Manitoba, Canada. Our results showed that only variation in dissolved oxygen levels affected feeding activity by terns. Since there was no relationship between bird and fish abundance either within or among years, these results suggest that it is the availability of prey (i.e. the upward movement of fish into the water column) and not their abundance per se that influences the number of avian predators present and hence the risk of predation to fish. These data demonstrate how the physical environment of aquatic ecosystems can impact terrestrial avian predators, and the link that exists between the physical environment and predator-prey interactions. [ABSTRACT FROM AUTHOR]

The likelihood of encountering a predator influences prey behavior and spatial distribution such that non-consumptive effects can outweigh the influence of direct predation. Prey species are thought to filter information on perceived predator encounter rates in physical landscapes into a landscape of fear defined by spatially explicit heterogeneity in predation risk. The presence of multiple predators using different hunting strategies further complicates navigation through a landscape of fear and potentially exposes prey to greater risk of predation. The juxtaposition of land cover types likely influences overlap in occurrence of different predators, suggesting that attributes of a landscape of fear result from complexity in the physical landscape. Woody encroachment in grasslands furnishes an example of increasing complexity with the potential to influence predator distributions. We examined the role of vegetation structure on the distribution of two avian predators, Red-tailed Hawk ( Buteo jamaicensis) and Northern Harrier ( Circus cyaneus), and the vulnerability of a frequent prey species of those predators, Northern Bobwhite ( Colinus virginianus). We mapped occurrences of the raptors and kill locations of Northern Bobwhite to examine spatial vulnerability patterns in relation to landscape complexity. We use an offset model to examine spatially explicit habitat use patterns of these predators in the Southern Great Plains of the United States, and monitored vulnerability patterns of their prey species based on kill locations collected during radio telemetry monitoring. Both predator density and predation-specific mortality of Northern Bobwhite increased with vegetation complexity generated by fine-scale interspersion of grassland and woodland. Predation pressure was lower in more homogeneous landscapes where overlap of the two predators was less frequent. Predator overlap created areas of high risk for Northern Bobwhite amounting to 32% of the land area where landscape complexity was high and 7% where complexity was lower. Our study emphasizes the need to evaluate the role of landscape structure on predation dynamics and reveals another threat from woody encroachment in grasslands. [ABSTRACT FROM AUTHOR]

The adzebills (Aptornithidae) were an ancient endemic lineage of large flightless Gruiformes that became extinct shortly after Polynesian settlement of New Zealand. The diet and ecology of these enigmatic birds has long been a matter for conjecture, but recent stable isotope analyses of bones of the North Island adzebill (Aptornis otidiformis) have indicated that adzebills may have been predatory. Here, we add to our understanding of adzebill ecology by providing the first stable isotope analyses of South Island adzebill (A. defossor) bones from two Holocene deposits. We interpret the results within frameworks of stable isotope measurements on bones of faunal species with known diets and from the same deposits (thereby mitigating regional effects on isotope values). Our results strongly support the hypothesis that adzebills had a high trophic position. Considered alongside the unique skeletal adaptations of adzebills and the distribution of the species during the Holocene, we suggest that adzebills were most likely terrestrial predators restricted to dry podocarp forests and may have specialised in dismantling rotting logs to obtain invertebrates and/or excavating burrowing animals such as tuatara or the chicks of burrow-nesting birds. [ABSTRACT FROM AUTHOR]

Context: Despite increasing evidence that landscape composition and configuration strongly influence the community structure of potential pest-regulators, landscape structure has seldom been explicitly linked with the rate and magnitude of pest-control services. Objectives and methods: We conducted a systematic literature review evaluating 158 relevant studies to: (1) characterize our existing understanding of the empirical relationships between landscape structure and avian-mediated insect pest control services in agricultural systems, (2) identify gaps in our current understanding, and (3) develop a conceptual model of landscape structural influences on avian-mediated pest control. Results and discussion: We found on-farm pest suppression by birds was often higher in landscapes with higher native habitat cover, higher compositional heterogeneity, and in agricultural patches in closer proximity to native habitats. We identified more than 200 bird species that provide pest control services across both temperate and tropical regions. While most avian predators are habitat-generalist species, a substantial fraction of pest control services in tropical regions was mediated by habitat-dependent species, suggesting a link between conservation management and maintenance of pest control services. We identified a three-part research agenda for future investigations of the relationships between landscape structure and avian-mediated pest control, focusing on an improved understanding of mechanisms related to: (1) predator-prey interactions and landscape modulation of trophic relationships, (2) bird dispersal ability and landscape connectivity, and (3) cross-habitat spillover of habitat-dependent avian predators. Implications: These findings can be applied to efforts to manage and design landscapes capable of supporting both biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

True bugs are generally considered to be well protected against bird predation. Sympatric species that have similar warning coloration are supposed to form a functional Müllerian mimetic complex avoided by visually oriented avian predators. We have tested whether these assumptions hold true for four species of European red-and-black heteropterans, viz. Pyrrhocoris apterus, Lygaeus equestris, Spilostethus saxatilis, and Graphosoma lineatum. We found that individual species of passerine birds differ in their responses towards particular bug species. Great tits (Parus major) avoided all of them on sight, robins (Erithacus rubecula) and yellowhammers (Emberiza citrinella) discriminated among them and attacked bugs of some species with higher probability than others, and blackbirds (Turdus merula) frequently attacked bugs of all the tested species. Different predators thus perceive aposematic prey differently, and the extent of Batesian-Müllerian mimetic complexes and relations among the species involved is predator dependent.

Increased raptor and corvid abundance has been documented in landscapes fragmented by man-made structures, such as fence posts and power lines. These vertical structures may enhance raptor and corvid foraging and predation efficiency because of increased availability of perch, nesting, and roosting sites. Concomitantly, vertical structures, in particular power distribution lines, have been identified as a threat to sage-grouse (Centrocercus spp.) conservation. To mitigate potential impacts of power distribution lines on sage-grouse and other avian species, the electrical power industry has retrofitted support poles with perch deterrents to discourage raptor and corvid use. No published information is available regarding efficacy of contemporary perch deterrents on avian predator use of lower-voltage power distribution lines. We evaluated efficacy of 5 perch deterrents mounted on support poles of an 11-km section of a 12.5-kV distribution line that bisected occupied Gunnison sage-grouse (Centrocercus minimus) habitat in southeastern Utah, USA. Perch deterrents were mounted on the line in November-December 2006 following a random replicated block design that included controls. During 168 hours and 84 hours of direct observation in 2007 and 2008, respectively, we recorded 276 and 139 perching events of 7 potential avian predators of sage-grouse. Golden eagles (Aquila chrysaetos) were the dominant species we recorded during both years. We did not detect any difference in perching events by perch deterrent we evaluated and controls (P > 0.05). Perch deterrents we evaluated were not effective because of inherent design and placement flaws. Additionally, previous pole modifications that mitigated avian electrocutions provided alternative perches. We did not record any raptor or corvid electrocutions or direct predation on Gunnison sage-grouse. The conclusions of this study can be applied by conservation groups and power companies to future management of power distribution lines within areas inhabited by species sensitive to man-made vertical structures. [ABSTRACT FROM AUTHOR]

The cane toad (Bufo marinus ), a large, toxic, American anuran, was introduced to Australia in 1935. Populations of many of Australia's reptiles (snakes, varanid lizards, crocodiles) and carnivorous mammals (dasyurid marsupials) have declined because these predators are killed by the toad's powerful toxins. In contrast to these well-studied species, little is known about the cane toads impacts on Australian birds. We reviewed published and unpublished data on behavioral interactions between Australian avian predators and cane toads and collated distributional and dietary information to identify avian taxa potentially at risk from cane toad invasion. Cane toads are sympatric with 172 frog-eating bird species in Australia, and an additional 8 bird species overlap with the predicted future range of the toad. Although many bird species thus are potentially at risk, behavioral observations suggest the risk level is generally low. Despite occasional reports of Australian birds being killed when they ingest cane toads, most birds either ignore toads or survive the predation event. The apparently higher tolerance of Australian birds to toad toxins, compared with Australian reptiles and marsupials, may reflect genetic exchange between Australian birds and Asian populations that encounter other bufonid species regularly and hence have evolved the capacity to recognize or tolerate this toxic prey. [ABSTRACT FROM AUTHOR]

The article reports on the research conducted by Francis K. Wiese and colleagues on management of predator-prey relationship of birds and salmonids in the Columbia River basin. It shows that predator-prey relationships are altered as a result of human activities. In Columbia River basin, piscivorous predators have been implicated in contributing to lack of recovery of several endangered anadromous salmonids and control systems are instituted against piscine and avian species. Researchers employed the use of bioenergetics approach to estimate the consumption of salmonid smolts by waterbirds. Studies reveal that smolts survival could be maximized by deterring birds from the river when smolts are present, allowing bird presence after the diet switch to act as a tool for predator control.

A new high-voltage transmission line in north-central Nevada, USA, was considered a potential threat to greater sage-grouse (Centrocercus urophasianus) because avian predators are attracted to and hunt from elevated perches. As a mitigation measure, perch deterrents were installed on the transmission line towers at the time of construction; in addition, 2 existing high-voltage transmission lines were retrofitted with deterrents. Previous published studies have investigated the efficacy of perch deterrents in preventing or reducing electrocution of avian predators and fecal contamination of insulators, but none have evaluated deterrents as a means of eradicating perching on towers. We conducted point transect surveys and perching-duration observations of corvids and raptors and determined that although perch deterrents did not prevent perching, the perching duration of raptors on the deterrents was reduced compared to other perching substrates. Perching of raptors indicated that some hunting most likely took place from the towers; therefore, the deterrents did not completely obviate the threat that avian predators posed to greater sage-grouse. Although the deterrents reduced the probability of avian predators perching on the towers, avian predators overcame the deterrents to take advantage of the height of the towers where no other perches of similar height existed. The perch deterrents as designed did not have the desired short-term effect on avian predators, but further monitoring may reveal longer-term effects and distinguish perching behaviors specific to different species of avian predators. [ABSTRACT FROM AUTHOR]

1. Patch structural complexity affects local species richness and population densities. Anthropogenic disturbance may alter complexity and heterogeneity, resulting in changes in community structure. Most studies in this area have dealt with human-induced habitat degradation. We investigated a converse situation, in which anthropogenic activity increases productivity and complexity of an arid habitat. 2. Recently, large areas in the northern Negev Desert have been altered: a series of contour catchments was constructed to accumulate run-off to support planted trees. We examined the effect of patch alteration by focusing on the lizard assemblage in the planted plots. Seven pairs of plots were established, one plot from each pair in a natural area and the other in an adjacent, altered slope. Lizards were captured using pitfall traps and environmental parameters were measured. To isolate the effects of trees as perches for avian predators, we ‘planted’ artificial trees in a loess plain and investigated the effect on an endemic lizard. 3. The structure of the lizard assemblage in the planted plots differed from that of the natural plots. Planted plots had a higher proportion of Mediterranean lizards and fewer desert species. Two local lizard species disappeared from the mosaic area of planted and natural plots. In addition, avian predators spent longer time in the artificial tree plots and reduced the lizard density compared to the natural plots. 4. The modification to the habitat generated only moderate changes in structure of the natural vegetation and this could not account for the observed changes in the lizard assemblage. Changes in the spatial use of the plots by avian predators was identified as the mechanism behind the observed distribution of lizard species. 5. Synthesis and applications. We argue that anthropogenic habitat modifications such as afforestation, urbanization, etc., can induce indirect biotic effects that may change the way and the scale at which different species respond to the habitat change. Such structural alteration may lead to species replacement and even to local extinction of specialist species. In order to protect biodiversity during large-scale management projects, alteration of biotic interactions should be considered in advance and large unaltered patches should be protected, otherwise indirect effects might cause greater impacts than the structural manipulation itself. [ABSTRACT FROM AUTHOR]

The persistence of Müllerian mimicry and geographically distinct wing patterns, as observed in many Heliconius species (Lepidoptera: Nymphalidae), is difficult to explain from a predator's perspective: predator selection against locally rare patterns must persist despite avoidance learning. Maintaining spatial color-pattern polymorphism requires local pattern avoidance, fine-scale discrimination among similar wing patterns, and repeated attacks on novel color patterns. I tested for these behaviors by presenting 80 adult rufous-tailed jacamars (Galbula ruficauda) with three morphs of Heliconius butterflies, and then presenting the same suite of butterflies to 46 of these jacamars between four and 429 days later. These trials offer the first direct evidence of the selective predator behavior required to maintain aposematic polymorphism: jacamars avoid local aposematic morphs while repeatedly attacking similar but novel morphs over time. [ABSTRACT FROM AUTHOR]

Sublethal burdens of lead impair behaviors critical to survival in a variety of animals. In a test arena, I measured refuge-seeking behaviors of adult, male, lined shore crabs from lead-free and lead-contaminated sites. The body sizes of the test groups did not differ although the mean total body lead burdens differed by over 2,300%. A lead-contaminated environment does not appear to affect growth. Each of the 31 crabs had at least six trials in the arena. The fraction of trials with more than one pause, number of pauses per trial, mean time per pause, and the fraction of time a crab spent in pauses did not differ between groups. The absence of behavioral effects of the lead burdens may be because a large portion of the lead burden was sequestered in the carapace. The neurological and other soft tissues would then have lower levels of lead. Predators that ingest primarily soft tissues would have little exposure to the lead burden of these crabs. Those that also ingest the carapace may benefit from its high calcium content that inhibits lead uptake from the gut, regardless of the location of lead in the crab body. [ABSTRACT FROM AUTHOR]

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