The predatory ecology of Deinonychus and the origin of flapping in birds

Most non-avian theropod dinosaurs are characterized by fearsome serrated teeth and sharp recurved claws. Interpretation of theropod predatory ecology is typically based on functional morphological analysis of these and other physical features. The notorious hypertrophied 'killing claw' on pedal digit (D) II of the maniraptoran theropod Deinonychus (Paraves: Dromaeosauridae) is hypothesized to have been a predatory adaptation for slashing or climbing, leading to the suggestion that Deinonychus and other dromaeosaurids were cursorial predators specialized for actively attacking and killing prey several times larger than themselves. However, this hypothesis is problematic as extant animals that possess similarly hypertrophied claws do not use them to slash or climb up prey. Here we offer an alternative interpretation: that the hypertrophied D-II claw of dromaeosaurids was functionally analogous to the enlarged talon also found on D-II of extant Accipitridae (hawks and eagles; one family of the birds commonly known as "raptors"). Here, the talon is used to maintain grip on prey of subequal body size to the predator, while the victim is pinned down by the body weight of the raptor and dismembered by the beak. The foot of Deinonychus exhibits morphology consistent with a grasping function, supportive of the prey immobilisation behavior model. Opposite morphological trends within Deinonychosauria (Dromaeosauridae + Troodontidae) are indicative of ecological separation. Placed in context of avian evolution, the grasping foot of Deinonychus and other terrestrial predatory paravians is hypothesized to have been an exaptation for the grasping foot of arboreal perching birds. Here we also describe "stability flapping", a novel behaviour executed for positioning and stability during the initial stages of prey immobilisation, which may have been pivotal to the evolution of the flapping stroke. These findings overhaul our perception of predatory dinosaurs and highlight the role of exaptation in the evolution of novel structures and behaviours.     

Evidence for Convergent Evolution in Gape Morphology of the Bat Hawk (Macheiramphus alcinus) with Swifts,Swallows, and Goatsuckers

Gape morphology has been linked to feeding and breeding ecology in raptors, according to the ingestion rate hypothesis. Mammal feeding raptors have larger gapes, allowing them to ingest prey more rapidly than bird feeders, which have evolved smaller average body sizes and gapes to capture more agile prey. One highly derived raptor, however, the Bat Hawk (Macheiramphus alcinus), specializes on colonial bats and swiftlets concentrated daily in a limited temporal window by capturing and swallowing them whole in flight. We hypothesized that the gape of the Bat Hawk evolved to feed rapidly on agile vertebrates limited temporally. We predicted that the gape of the Bat Hawk would be significantly larger than the gape of other raptors, more closely resembling the gapes of swifts (Apodidae), swallows (Hirundinidae), and goatsuckers (Caprimulgiformes). We measured gape area of the lower mandible in museum specimens representing 138 bird species in six orders. We also compared gape area by prey type in over 100 raptor species in three orders. We predicted that insectivorous raptors would exhibit gapes similar to mammal feeders but would differ from bird feeders because insects are not agile prey. The Bat Hawk had the largest gape of any raptor and more closely resembled the gape of insectivorous birds, which also swallow prey whole in flight. The evolution of an enlarged gape may have permitted the Bat Hawk to exploit a previously unrealized ecological niche. Gapes of bird feeding raptors were smaller than in mammal and insect feeders, supporting the ingestion rate hypothesis.     

Messy eaters: Swabbing prey DNA from the exterior of inconspicuous predators when foraging cannot be observed

Complex coevolutionary relationships among competitors, predators, and prey have shaped taxa diversity, life history strategies, and even the avian migratory patterns we see today. Consequently, accurate documentation of prey selection is often critical for understanding these ecological and evolutionary processes. Conventional diet study methods lack the ability to document the diet of inconspicuous or difficult‐to‐study predators, such as those with large home ranges and those that move vast distances over short amounts of time, leaving gaps in our knowledge of trophic interactions in many systems. Migratory raptors represent one such group of predators where detailed diet studies have been logistically challenging. To address knowledge gaps in the foraging ecology of migrant raptors and provide a broadly applicable tool for the study of enigmatic predators, we developed a minimally invasive method to collect dietary information by swabbing beaks and talons of raptors to collect trace prey DNA. Using previously published COI primers, we were able to isolate and reference gene sequences in an open‐access barcode database to identify prey to species. This method creates a novel avenue to use trace molecular evidence to study prey selection of migrating raptors and will ultimately lead to a better understanding of raptor migration ecology. In addition, this technique has broad applicability and can be used with any wildlife species where even trace amounts of prey debris remain on the exterior of the predator after feeding.     

Birds at the Winter Feeder do not Recognize an Artificially Coloured Predator

It is supposed that coloration may affect the recognition of predators by prey species; nevertheless, the significance of the coloration and its particular components in the recognition process remains unknown. We presented dummies of the European sparrowhawk (Accipiter nisus) with changed body coloration, but with all other typical features preserved (body size and shape, beak, eyes, legs), to great tits (Parus major) and blue tits (Cyanistes caeruleus) visiting a winter feeder. A pigeon (Columba livia f. domestica) dummy was used as a harmless control. Neither tit species showed passive avoidance in the presence of a dummy with an artificial, violet‐white chequered coloration. They obviously did not consider such an object to be a predator despite the presence of the raptor beak, eyes and talons. Sparrowhawk dummies with the coloration completely changed (altered with those of a harmless European robin) or with the typical colour feature removed (barred pattern on the underparts) were considered to be as dangerous as the unmodified sparrowhawk. We discuss the possibility that the effect of salient raptor‐like features such as beak shape, eye coloration, and leg and talons shape overwhelmed the effect of body coloration in these cases. Birds visiting the feeder probably were able to generalize the vigilance towards the sparrowhawk to other realistically coloured dummies, but not to the non‐natural dummy.     

Musculoskeletal underpinnings to differences in killing behavior between North American accipiters (Falconiformes: Accipitridae) and falcons (Falconidae)

Accipiters (Accipiter spp.) and falcons (Falco spp.) both use their feet to seize prey, but falcons kill primarily with their beaks, whereas accipiters kill with their feet. This study examines the mechanistic basis to differences in their modes of dispatching prey, by focusing on the myology and biomechanics of the jaws, digits, and distal hindlimb. Bite, grip, and distal hindlimb flexion forces were estimated from measurements of physiological cross-sectional area (PCSA) and indices of mechanical advantage (MA) for the major jaw adductors, and digit and tarsometatarsal flexors. Estimated bite force, total jaw adductor PCSA, and jaw MA (averaged over adductors) tended to be relatively and absolutely greater in falcons, reflecting their emphasis on biting for dispatching their prey. Differences between genera in estimated grip force, total digit flexor PCSA, and digit MA (averaged over inter-phalangeal joints and digits) were not as clear-cut; each of these parameters scaled positively allometric in accipiters, which may reflect the scaling of both prey size, and the proportion of mammalian prey consumed by this lineage with increasing body size. Estimated tarsometatarsal force was greater in falcons than in accipiters, due to their greater MA, which may reflect selection for incurring greater forces during prey strikes. Conversely, the comparatively lower tarsometatarsal MA in accipiters reflects their capacity for greater foot speed potentially necessary for grasping elusive prey. Thus, this study elucidates how differences in jaw and hindlimb musculoskeletal morphology of accipiters and falcons are reflected in differences in their killing modes, and through differences in their force-generating capacities.     

Prey handling in raptors in relation to their morphology and feeding niches

Most raptors take large prey for their size compared to other birds, but tear the prey apart into small morsels before swallowing. Little is known about how the efficiency of this prey handling varies among raptors, and how it relates to their feeding niches, diets and gape dimensions. We offered 202 mammalian and 224 avian prey items to 37 wild raptors kept temporarily in captivity, representing ten species and three orders. Feeding efficiency was measured as the proportion of a prey item that was ingested. The proportion of a prey item ingested was larger for mammalian than for avian prey, declined with prey size, increased with raptor size, and was larger for typical vole feeders (with shorter and wider bills) than typical bird feeders (with longer and narrower bills). The proportion of a prey item ingested was not related to raptor sex when controlling for focal raptor body mass. The probability that the head of a prey was ingested was higher if the prey was a mammal than if it was a bird, whereas the opposite was the case for the entrails of a prey. The results suggest that the traditional use of prey remains to estimate raptor diets may lead to severe biases, the magnitude of which would depend on prey type and size, raptor sex, species and order, and raptor feeding niche. Failure to correct for uneaten remains of a prey would lead to overestimating the profitability of large prey, and in particular of large avian prey. The results are consistent with the idea that vole feeders can afford to have a well‐developed digestive tract, and thus swallow prey in large pieces, because they pounce on prey from above. Bird feeders, however, must ingest food in smaller pieces because they have smaller guts as a result of selection to keep the body mass low to capture agile prey.     

A comparison of digestive efficiency in birds of prey

Differences in how raptors hunt and what they catch are correlated with size-independent differences in length of the small intestine, the region of the digestive tract responsible for food absorption. The study examined the functional significance of these differences among ten raptor species. Dry matter apparent digestive efficiency was calculated for each species fed a diet of day-old cockerels. For Falconiformes and Strigiformes, efficiencies varied between 75% and 82%, digestive efficiency being positively correlated with intestine length.
Generalist species, with a wide prey spectrum and feeding on relatively easily caught prey and carrion, had long intestines and high digestive efficiencies. Raptors specializing on fast-moving, avian prey had short intestines and reduced digestive efficiency. The Peregrine Falco peregrinus and the Common Buzzard Buteo buteo were used as examples of specialist and generalist feeders, respectively. Rabbit and pigeon were fed to both. Buzzards digested both diets more efficiently than Peregrines. Body-mass changes were used to examine the nutritional value of the two diets to each species. Buzzards gained body-mass when eating rabbit, Peregrines lost mass. Both species gained mass when feeding on pigeon. It seems that consideration of diet quality, not just quantity, is essential in understanding raptor food requirements. Generalist raptors have high efficiencies on several diets, specialists compensate for their reduced efficiency by eating food of high nutritional quality. Various aspects of prey quality are examined.     

The effects of raptor predation on wintering wader populations at the Tyningharne estuary, southeast Scotland

Raptor predation on waders was studied by direct observation of raptors hunting a known wader population and subsequent recovery of dead waders. In each of three winters, raptor predation was shown to be the most significant cause of mortality in most small wader species, Sparrowhawks Accipiter nisus , Merlins Falco columbarius and Peregrines F. pere-grinus attacked waders with a success rate of 11.6%. 8.8% and 6.8%, respectively. Most waders attacked or found dead were Redshank Tringa totanus and Dunlin Calidris alpina; most were killed by Sparrowhawks. Kleptoparasitism of raptors carrying prey by Carrion Crows Corvus corone significantly increased the winter mortality of some waders. Redshank populations were most affected by raptor predation: over 50% of the total population (which was found to be closed during most of the winter) and over 90% of the juvenile population were taken in two winters: juvenites were more likely to be killed by raptors.     

Birds of prey as limiting factors of gamebird populations in Europe: a review

Whether predators can limit their prey has been a topic of scientific debate for decades. Traditionally it was believed that predators take only wounded, sick, old or otherwise low-quality individuals, and thus have little impact on prey populations. However, there is increasing evidence that, at least under certain circumstances, vertebrate predators may indeed limit prey numbers. This potential role of predators as limiting factors of prey populations has created conflicts between predators and human hunters, because the hunters may see predators as competitors for the same resources. A particularly acute conflict has emerged over the past few decades between gamebird hunters and birds of prey in Europe. As a part of a European-wide research project, we reviewed literature on the relationships between birds of prey and gamebirds. We start by analysing available data on the diets of 52 European raptor and owl species. There are some 32 species, mostly specialist predators feeding on small mammals, small passerine birds or insects, which never or very rarely include game animals (e.g. hares, rabbits, gamebirds) in their diet. A second group (20 species) consists of medium-sized and large raptors which prey on game, but for which the proportion in the diet varies temporally and spatially. Only three raptor species can have rather large proportions of gamebirds in their diet, and another seven species may utilise gamebirds locally to a great extent. We point out that the percentage of a given prey species in the diet of an avian predator does not necessarily reflect the impact of that predator on densities of prey populations. Next, we summarise available data on the numerical responses of avian predators to changing gamebird numbers. In half of these studies, no numerical response was found, while in the remainder a response was detected such that either raptor density or breeding success increased with density of gamebirds. Data on the functional responses of raptors were scarce. Most studies of the interaction between raptors and gamebird populations give some estimate of the predation rate (per cent of prey population taken by predator), but less often do they evaluate the subsequent reduction in the pre-harvest population or the potential limiting effect on breeding numbers. The few existing studies indicate that, under certain conditions, raptor predation may limit gamebird populations and reduce gamebird harvests. However, the number and extent of such studies are too modest to draw firm conclusions. Furthermore, their geographical bias to northern Europe, where predator-prey communities are typically simpler than in the south, precludes extrapolation to more diverse southern European ecosystems. There is an urgent need to develop further studies, particularly in southern Europe, to determine the functional and numerical responses of raptors to gamebird populations in species and environments other than those already evaluated in existing studies. Furthermore, additional field experiments are needed in which raptor and possibly also mammalian predator numbers are manipulated on a sufficiently large spatial and temporal scale. Other aspects that have been little studied are the role of predation by the non-breeding part of the raptor population, or floaters, on the breeding success and survival of gamebirds, as well as the effect of intra-guild predation. Finally there is a need for further research on practical methods to reduce raptor predation on gamebirds and thus reduce conflict between raptor conservation and gamebird management.     

Microhabitat use and behavior of voles under weasel and raptor predation risk: predator facilitation?

An example of predator facilitation is that a microhabitat shiftin a prey species induced by one predator increases the probabilityof the prey falling victim to other predators. Least weasels(Mustela nivalis) hunt in dense plant cover, whereas kestrels(Falco tinnunculus) hunt in habitats with sparse plant cover.Field voles (Microtus agrestis), the main food of weasels andkestrels, prefer open country with a high grass layer. We simulateda multipredator environment in an aviary (3.0 x 4.8 x 2.2 m)to find out whether predator facilitation plays a role in theinteractions between voles, small mustelids, and raptors. Ineach replicate, we placed a field vole in a pen including sidesof high and low grass layers (cover and open). In a predator-freesituation, voles preferred cover but shifted to open when aweasel was introduced to cover. In the presence of a kestrel,voles occupied cover and decreased their mobility. In the presenceof a weasel plus a kestrel, voles behaved as under the kestrelrisk alone. Therefore, in these aviary circumstances, volesperceived the kestrel risk as greater than the weasel risk.Predator facilitation in the assemblage of predators subsistingon rodent prey may contribute to the crash of the four-yearvole cycle: microhabitat shift due to an avoidance of weaseljaws may drive voles to raptor talons.     

The complete mitochondrial genome of Japanese sparrowhawk (Accipiter gularis) and the phylogenetic relationships among some predatory birds

Phylogenetic relationships among raptors, especially various groups are rather complex and controversial. We determined the complete mtDNA of Japanese sparrowhawk, and estimated phylogenetic trees based on the complete mtDNA alignment of it and 36 other raptor species, to clarify raptor phylogenetics. Phylogenetic trees were also estimated using a multiple sequence alignment of 12S rRNA and 16S rRNA from 81 typical species in GenBank, to further clarify the phylogenetic relationships of several groups among the raptors. The new mtDNA is a circular molecule, 17 917 bp in length, containing the 37 typical genes, with a pseudo-control region. ATG is generally the start codon, TAA is the most frequent stop codon. All tRNAs can be folded into canonical cloverleaf secondary structures except for tRNA^{Ser (AGY)} and tRNA^{Leu (CUN)}, which are missing the “DHU” arm. Phylogenetic relationships demonstrate that raptors can be divided into four branches: Accipitriformes, Falconiformes, Strigiformes and Caprimulgiformes in this study. We suggest that Accipitriformes should to be an independent order, Accipitriformes. The results also indicate that Accipitriformes contains three clades: Accipitridae, Pandionidae and Sagittariidae. Strigiformes includes species from Tytonidae and Strigidae. Caprimulgiformes contains Aegothelidae and Caprimulgidae.     

Effects of predator removal on vertebrate prey populations: birds of prey and small mammals

We studied the effects of removal of breeding nomadic avian predators (the kestrel, Falco tinnunculus and Tengmalm's owl, Aegolius funereus) on small mammals (voles of the genera Microtus and Clethrionomys and the common shrew, Sorex araneus) during 1989–1992 in western Finland to find out if these predators have a regulating or limiting impact on their prey populations. We removed potential breeding sites of raptors from five manipulation areas (c. 3 km² each), whereas control areas had nest-boxes in addition to natural cavities and stick-nests. Densities of small mammals were monitored by snap-trapping in April, June, and August, and densities of mammalian predators (the least weasel, Mustela nivalis nivalis, the stoat, M. erminea and the red fox, Vulpes vulpes) by snow tracking in early spring and late autumn. The yearly mean number of raptor breeding territories was 0.2–1.0 in reduction areas and 3.0–8.2 in control areas. Breeding raptors alone did not regulate prey populations in the long term, but probably caused short-term changes in the population dynamics of both the main prey, the sibling vole (Microtus rossiaemeridionalis) and an alternative prey (the common shrew). The densities of an alternative prey, the bank vole (Clethrionomys glareolus) decreased in raptor reduction areas, most likely due to increased least weasel predation pressure in the absence of breeding avian predators.     

Food partitioning between breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in southern Brazil.

I examined the diet of breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in an agrarian area of southern Brazil by analyzing regurgitated prey remains. The objective was to evaluate how these raptors, which differ markedly in their hunting activity periods (owls are nocturnal and kites diurnal), share their mammalian food component. 2,087 prey consumed by Barn Owls and 1,276 by White-tailed Kites were identified. They presented a high overlap of food-niches (Piankas index was 0.98). Based on the daily activity period of their main small mammal prey, a lower overlap would be expected. The crepuscular/nocturnal Mus musculus was the main prey for the diet of breeding Barn Owls (81%) and White-tailed Kites (63%). This small exotic rodent provided 63% of the small mammal biomass ingested by owls and 44% by kites. Larger native small mammals were also considered important for the diet of kites, mainly because of their biomass contribution. Although these raptors differ markedly in their hunting activity periods, Barn Owls and White-tailed Kites are very similar predators in southern Brazil, overlapping their diets.     

Raptors breeding on weaver nests in trees and on man-made structures

Several raptor species nest on top of large weaver nests. These weaver nests are usually sited in trees, but 11.7% of Red-billed Buffalo-Weaver Bubalornis niger and 25.7% of Sociable Weaver Philetairus socius nests occur on man-made structures. In an extensive literature search, a total of 16 raptor species were recorded as nesting on top of weaver nests. At least 10 raptor species used weaver nests built in trees. Seven raptor species used weaver nests on man-made sites and four raptor species only used weaver nests built on man-made sites. No owls have been recorded as using weaver nests on man-made sites. There are historical records of raptors nesting on top of weaver nests in trees, while nesting on top of weaver nests sited on man-made structures appears to be a more recent adaptation. Costs and benefits of nesting on man-made sites are briefly listed. Nesting on man-made sites may increase (by both weavers and raptors) and raptor researchers are encouraged to document cases of raptors nesting on weaver nests where these are placed in trees or artificial sites, so that there is a record of changes in frequency of nest site usage by raptors.     

Bats as prey of diurnal birds: a global perspective

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Complete mtDNA genome of Otus sunia (Aves,Strigidae) and the relaxation of selective constrains on Strigiformes mtDNA following evolution

Most of owls are nocturnal raptor and usually use their soft and fluffy feathers to flight silently to catch prey while other diurnal raptors prefer fierce attack and swift flight. For energy cost of these different hunting strategies can be greatly different, we speculate that mitochondrial gene of owls may undergo a different evolution pattern following raptors evolution. To test our hypothesis, we sequenced the mtDNA genome of Otus sunia and calculated the ratio of nonsynonymous to synonymous nucleotide substitutions (ω, Ka/Ks, dN/dS) of raptors. The mtDNA genome of O. sunia was 17,609 bp in length, containing 13 PCGs, 2 ribosomal RNAs, 22 transfer RNAs and a control region. Secondly structure of tRNAs and rRNAs were predicted and conserved sequence blocks (CSBs) on control region were identified. The Bayesian inference tree and maximum likelihood tree based on 13 PCGs and 2 rRNAs suggested the owls were related to other raptors. Finally, calculation of ω-values of each owls and other raptors mtDNA PCGs indicated that owls accumulated more nonsynonymous nucleotide substitutions relative to synonymous substitutions compared to other raptors. For mtDNA PCGs associated with energy metabolism, this finding may reveal the degeneration of flight abilities of owls.     

Grasping kinematics from the perspective of the individual digits: a modelling study

Grasping is a prototype of human motor coordination. Nevertheless, it is not known what determines the typical movement patterns of grasping. One way to approach this issue is by building models. We developed a model based on the movements of the individual digits. In our model the following objectives were taken into account for each digit: move smoothly to the preselected goal position on the object without hitting other surfaces, arrive at about the same time as the other digit and never move too far from the other digit. These objectives were implemented by regarding the tips of the digits as point masses with a spring between them, each attracted to its goal position and repelled from objects' surfaces. Their movements were damped. Using a single set of parameters, our model can reproduce a wider variety of experimental findings than any previous model of grasping. Apart from reproducing known effects (even the angles under which digits approach trapezoidal objects' surfaces, which no other model can explain), our model predicted that the increase in maximum grip aperture with object size should be greater for blocks than for cylinders. A survey of the literature shows that this is indeed how humans behave. The model can also adequately predict how single digit pointing movements are made. This supports the idea that grasping kinematics follow from the movements of the individual digits.     

Inadequacy of activity time as a niche difference: the case of diurnal and nocturnal raptors

Summary It has been assumed that differences in activity time of diurnal (Falconiform) and nocturnal (Strigiform) raptors reduce competition for food by giving them access to different prey resources. Consequently, dietary similarity should be greater between synchronously active raptors (either diurnal or nocturnal) than between asynchronous ones (diurnal versus nocturnal). Using five collective raptor assemblages I tested the hypothesis that the statistical distribution of food overlaps between synchronous raptors (Falconiform x Falconiform and Strigiform x Strigiform combined) should be composed of larger figures than that obtained from asynchronous pairs (Falconiform x Strigiform). Both a conservative (Kolmogorov-Smirnov test with Chisquare approximation) and a powerful (Mann-Whitney U-test) nonparametric procedure were used to deal with the problem of the degrees of freedom to be assigned to non-indepedent observations such as overlaps. The tests consistently failed to reject the null hypothesis, thus pointing to the inadequacy of temporal segregation as a means to partition prey resources between diurnal and nocturnal raptors. I propose that this can be accounted for by two factors, acting singly or in combination: a) that both Falconiforms and Strigiforms extend their hunting activities to crepuscular hours thus sharing prey of that activity period; b) that reputedly diurnal and nocturnal prey become vulnerable to predators of asynchronous hunting time by extending their activities in the field. Based on records of interspecific territoriality, prevation, and interference competition I propose that the evolution of nocturnality in Strigiforms might be more clearly related to interference interactions rather than exploitation competition with Falconiforms.     

Characterization,Polymorphism, and Evolution of MHC Class II B Genes in Birds of Prey

During the last decade, the major histocompatibility complex (MHC) has received much attention in the fields of evolutionary and conservation biology because of its potential implications in many biological processes. New insights into the gene structure and evolution of MHC genes can be gained through study of additional lineages of birds not yet investigated at the genomic level. In this study, we characterized MHC class II B genes in five families of birds of prey (Accipitridae, Pandionidae, Strigidae, Tytonidae, and Falconidae). Using PCR approaches, we isolated genomic MHC sequences up to 1300 bp spanning exons 1 to 3 in 26 representatives of each raptor lineage, finding no stop codons or frameshift mutations in any coding region. A survey of diversity across the entirety of exon 2 in the lesser kestrel Falco naumanni reported 26 alleles in 21 individuals. Bayesian analysis revealed 21 positively selected amino acid sites, which suggests that the MHC genes described here are functional and probably expressed. Finally, through interlocus comparisons and phylogenetic analysis, we also discuss genetic evidence for concerted and transspecies evolution in the raptor MHC.     

Reduced abundance of raptors in radioactively contaminated areas near Chernobyl

The negative ecological effects of radioactive contamination around Chernobyl have recently been suggested to be moderate and declining because of an increasing number of anecdotal observations of several species of rare animals including predators. However, these claims were not based on empirical evidence. Radionuclides show bio-accumulation with trophic level, and the abundance of birds is depressed in radioactively contaminated areas around Chernobyl. Therefore, we predicted that birds of prey should be less abundant with increasing levels of radiation. Here, we use our long-term field data from 1991 to 2007 in three different analyses based on observations of raptors using standardized point counts, censuses during capture of barn swallows Hirundo rustica that habitually give alarm calls when a raptor is present, and line transects while driving on roads. Analyses suggest that the abundance of birds of prey is reduced in contaminated areas, and that there is evidence of a recent increase in abundance of raptors in less contaminated areas, but not in the most contaminated ones. Our findings suggest that birds of prey that are top level consumers in ecosystems suffer from reduced abundance in radioactively contaminated areas.