Birds Of Prey Research Articles

Through Hawks’ Eyes: Synthetically Reconstructing the Visual Field of a Bird in Flight

Birds of prey rely on vision to execute flight manoeuvres that are key to their survival, such as intercepting fast-moving targets or navigating through clutter. A better understanding of the role played by vision during these manoeuvres is not only relevant within the field of animal behaviour, but could also have applications for autonomous drones. In this paper, we present a novel method that uses computer vision tools to analyse the role of active vision in bird flight, and demonstrate its use to answer behavioural questions. Combining motion capture data from Harris’ hawks with a hybrid 3D model of the environment, we render RGB images, semantic maps, depth information and optic flow outputs that characterise the visual experience of the bird in flight. In contrast with previous approaches, our method allows us to consider different camera models and alternative gaze strategies for the purposes of hypothesis testing, allows us to consider visual input over the complete visual field of the bird, and is not limited by the technical specifications and performance of a head-mounted camera light enough to attach to a bird’s head in flight. We present pilot data from three sample flights: a pursuit flight, in which a hawk intercepts a moving target, and two obstacle avoidance flights. With this approach, we provide a reproducible method that facilitates the collection of large volumes of data across many individuals, opening up new avenues for data-driven models of animal behaviour.

Rapid and recent range collapse of Australia’s Red Goshawk Erythrotriorchis radiatus

ABSTRACT Australia’s Red Goshawk (Erythrotriorchis radiatus) is a taxonomically distinct raptor endemic to the tropics and sub-tropics of eastern and northern Australia, and the Australian mainland’s rarest bird of prey. Classified as Vulnerable when legislation was first enacted in 1992, the species’ status and distribution remain unclear, and it is possibly declining based on limited surveys. However, no comprehensive analysis of its range-wide population trends has ever been undertaken, creating a knowledge gap which potentially delays urgent conservation management. Here, we bridge that knowledge gap. We compile a comprehensive dataset of 1,679 occurrence records spanning the species’ historical range, develop a novel method that overcomes reporting biases centred around nest locations, then identify population trends between 1978 and 2020 at national, state, and regional scales. Our results suggest that the species has declined significantly across eastern Australia and is likely locally extinct in many regions. We estimate the Red Goshawk has disappeared from 34% of its breeding range over the last four decades, and probably persists at extremely low density, if at all, over an additional 29.7% of its breeding range. These results demonstrate the species’ declining population trajectory at multiple scales for the first time and provide further evidence for its up listing under Australian federal legislation to Endangered, using IUCN Red List criterion C2a(ii): small population size and decline. We recommend population surveys and monitoring coupled with targeted research to better understand population trajectories and determine which threats are driving this unique species’ decline.

Residues of an anthelmintic veterinary drug (closantel) detected in red foxes (Vulpes vulpes) in Scotland

The contamination of the environment by some veterinary medicines and their impact on wild animals is of increasing concern. However, there is a lack of information about their residues in wildlife. The sentinel animals most commonly used for monitoring the level of environmental contamination are birds of prey, and information on other carnivores and scavengers scarce. This study examined the livers from 118 foxes for residues of a range of 18 veterinary medicines (16 anthelmintic agents and 2 metabolites) used on farm livestock. The samples were collected from foxes, primarily in Scotland, shot during legal pest control activities conducted between 2014 and 2019. Closantel residues were detected in 18 samples, and the concentrations found ranged from 6.5 µgkg−1 to 1383 µgkg−1. No other compounds were found in significant quantities. The results show a surprising frequency and level of closantel contamination, raising concerns about both the route of contamination and the potential impacts on wild animals and the environment, such as the potential for significant wildlife contamination to contribute to the development of closantel-resistant parasites. The results also suggest that red fox (Vulpes vulpes) could be a useful sentinel species for detecting and monitoring some veterinary medicine residues in the environment.

Diet Composition of a Pair of Tyto furcata pratincola (American Barn Owl) in an Urban Park and Natural Area Fragment in South Florida

Tyto furcata pratincola (American Barn Owl) is a widespread bird of prey with great adaptability that can be found in partially urbanized areas. We examined the prey composition of a pair of American Barn Owls through dissection and analysis of a subset of cast pellets found at a roost site in an urban park in South Florida by comparing hair, bone, and teeth to online identification guides and museum specimens. The main identified prey species were rodents, with Sigmodon hispidus (Hispid Cotton Rat) accounting for 63.0% of all prey identified. Within the home range of these owls were 9 known colonies of endangered and common species of bats, but no evidence of depredation was found in the pellet analysis. Other small mammals, reptiles, and invertebrates made up the remainder of the diet, which is consistent with other similar studies in more natural settings.

Factors Influencing Wood Stork Prey Biomass in Roadside Created Wetlands

Infrastructure associated with a growing human population has disrupted hydrologic patterns and impacted wetland species such as Mycteria americana (Wood Stork). However, storks are commonly observed foraging along roadways in created wetlands and nesting in urban environments, suggesting that these areas may provide novel foraging habitat. We sampled both permanently inundated and ephemeral created wetlands to determine which hydrologic, vegetative, and physical attributes are associated with high stork prey biomass. Factors influencing stork prey biomass differed between permanently inundated and ephemeral created wetlands. Landscape-level vegetation and the physical properties of a wetland were more influential in permanently inundated ponds and canals whereas local-scale vegetation and hydrologic conditions were most influential in ephemeral ponds and swales. Furthermore, aquatic fauna biomass in permanently inundated created wetlands was 9x greater than in natural wetlands, and aquatic fauna biomass was even greater in the urban landscape. These findings suggest that created wetlands may serve as additional foraging habitat for Wood Storks. As natural wetlands continue to be lost and managed for human purposes, created wetlands should be considered in conservation plans and future management decisions for Wood Storks and other wading birds given their ability to produce wading bird prey.

Quantitative investigation of pengornithid enantiornithine diet reveals macrocarnivorous ecology evolved in birds by Early Cretaceous

The diet of Mesozoic birds is poorly known, limiting evolutionary understanding of birds' roles in modern ecosystems. Pengornithidae is one of the best understood families of Mesozoic birds, hypothesized to eat insects or only small amounts of meat. We investigate these hypotheses with four lines of evidence: estimated body mass, claw traditional morphometrics, jaw mechanical advantage, and jaw finite element analysis. Owing to limited data, the diets of Eopengornis and Chiappeavis remain obscure. Pengornis, Parapengornis, and Yuanchuavis show adaptations for vertebrate carnivory. Pengornis also has talons similar to living raptorial birds like caracaras that capture and kill large prey, which represents the earliest known adaptation for macrocarnivory in a bird. This supports the appearance of this ecology ∼35 million years earlier than previously thought. These findings greatly increase the niche breadth known for Early Cretaceous birds, and shift the prevailing view that Mesozoic birds mainly occupied low trophic levels.

Stakeholder discourse coalitions and polarisation in the hen harrier conservation debate in news media

Abstract Conservation conflicts are complex and can be deep‐rooted, with stakeholders holding entrenched policy positions. The actors involved producing verbal interconnected interactions that form policy debates. Thus, conservation debates can be viewed as network phenomena with stakeholders forming coalitions in support of, or opposition to, certain policies and practices. We used Discourse Network Analysis of print media to investigate the structure and dynamics of the stakeholder debate around the management of hen harriers Circus cyaneus, a bird of prey at the centre of a long‐standing conservation conflict in the United Kingdom. We aimed to determine whether the structure of discourse coalitions changed among the diverse aspects of the debate and whether the polarisation of the debate has changed through time. Our search and selection criteria led to the analysis of 737 statements within 131 newspaper articles published from August 1993 to December 2019. We show that, while the discourse network of the overall debate is quite unstructured, actors formed divergent coalitions when defining the conservation problem and its solutions. In contrast, discourses converged around reactions with positive or negative emotions in relation to events and issues of hen harrier conservation. Polarisation among actors has increased over time and peaked in the second half of the 2010s, concurrent with the release of the species recovery plan. Our study highlights the value of analysing discourse networks in conservation policy debates. Discourse networks reveal which aspects of any conservation problem cause stakeholders to converge or diverge and can identify periods of intensified debate that, ultimately, contribute to informing conflict mitigation and resolution processes. Read the free Plain Language Summary for this article on the Journal blog.

Temperament traits and glucocorticoid metabolites in tropical screech owl (Megascops choliba)

Animals constantly respond to stimuli from their surroundings, showing individual behavioral and endocrine differences upon perceived challenging and/or threatening stimuli. The temperament of 13 captive tropical screech owls (Megascops choliba) was defined by performing three challenge tests (novel space, taxidermist predator and trapping) to identify inter-individual differences and their possible relationship with the production of glucocorticoid metabolites (GCM). Feces samples of each bird were taken pre-and-post predator challenge to quantify GCM concentration by means of enzymatic immunoassay (EIA). The intensity of 13 adjectives selected to describe the owls' temperament was determined by three judges during behavioral testing. Only 3 adjectives (passive, vulnerable, and attentive) that showed strong inter-test and intra-individual correlation coefficients were considered. These adjectives were later grouped in a single dimension named “shyness”, enabling establishment of individual scores. The temperament of the owls showed correlation to post-predator challenge GCM levels (ρ = 0.79; p < 0.001). However, no significant differences were found in GCM levels before and after predator challenge. Our results both confirm that nocturnal behavior raptorial birds show positive relation between shy temper and adrenal response, and offer the non-invasive herein implemented methods for establishment of new hypotheses that will assess welfare of species kept under human care.

Consequences of arthropod community structure for an at-risk insectivorous bird.

Global declines in bird and arthropod abundance highlights the importance of understanding the role of food limitation and arthropod community composition for the performance of insectivorous birds. In this study, we link data on nestling diet, arthropod availability and nesting performance for the Coastal Cactus Wren (Campylorhynchus brunneicapillus sandiegensis), an at-risk insectivorous bird native to coastal southern California and Baja Mexico. We used DNA metabarcoding to characterize nestling diets and monitored 8 bird territories over two years to assess the relationship between arthropod and vegetation community composition and bird reproductive success. We document a discordance between consumed prey and arthropod biomass within nesting territories, in which Diptera and Lepidoptera were the most frequently consumed prey taxa but were relatively rare in the environment. In contrast other Orders (e.g., Hemiptera, Hymenoptera)were abundant in the environment but were absent from nestling diets. Accordingly, variation in bird reproductive success among territories was positively related to the relative abundance of Lepidoptera (but not Diptera), which were most abundant on 2 shrub species (Eriogonum fasciculatum, Sambucus nigra) of the 9 habitat elements characterized (8 dominant plant species and bare ground). Bird reproductive success was in turn negatively related to two invasive arthropods whose abundance was not associated with preferred bird prey, but instead possibly acted through harassment (Linepithema humile; Argentine ants) and parasite transmission or low nutritional quality (Armadillidium vulgare; "pill-bug"). These results demonstrate how multiple aspects of arthropod community structure can influence bird performance through complementary mechanisms, and the importance of managing for arthropods in bird conservation efforts.

Flight Type and Seasonal Movements Are Important Predictors for Avian Collisions in Wind Farms

Wind farms are an alternative energy source mitigating environmental pollution. However, they can have adverse effects, causing an increase in mortality for wildlife through collision with wind turbines. The aim of this study was to investigate the risks of bird collisions with wind turbines linked to species-specific variables. For this purpose, we have analysed the dead birds involved in wind farm collisions that were admitted to two rescue centres in Spain over a period of 16 years (2001–2016; full dataset: n = 3130). All the birds analysed in this study were killed by turbines in wind farms. We performed two linear models using all species and a reduced dataset (bird of prey and passerine having more than four collisions) that included group, seasonal movements, flight type, length, and the number of pairs for the Spanish and European populations. The coefficients and the percent of variance explained by each relevant variable were determined in the models and the real values were compared with predicted values to visualise the goodness of fit. We found that the flight type was the most important variable explaining 35% of the total variability for the model including all species and 29% for the reduced dataset respectively, followed by seasonal movement type (4%/17% respectively) and the Spanish population (4%/6%). Subsequent analyses suggested that species with hovering, song-flights and active soaring flights are more susceptible to collisions with wind farms, and that species showing partial migration have a significant peak of collisions across spring and autumn. The estimated species-specific collision index can help in modelling the theoretical risk of collision with wind turbines, depending on the species existing in the area and their predicted values of vulnerability, which is linked to flight types and seasonal movements.

The Dangerous Side of Being a Predator: Toxoplasma gondii and Neospora caninum in Birds of Prey.

Toxoplasma gondii and Neospora caninum are apicomplexan protozoa of major concern in livestock and T. gondii is also considered one of the major threats and a public health concern. These protozoa have a wide range of intermediate hosts, including birds. The present work aimed to assess the prevalence of these cyst-forming parasites in migratory and sedentary birds of prey. The skeletal muscle and myocardium of 159 birds of prey from Central Italy, belonging to 19 species and recovered across 6 Wildlife Recovery Centers/Care structures along the Italian migratory route, were collected specifically for molecular (PCR) and for histopathological analysis to detect T. gondii and N. caninum. For the molecular analysis, genomic DNA was extracted. The DNA was tested by sequence typing, targeting GRA6, 529 bp repeated element, B1, PK1, BTUB, SAG2, alt.SAG2, and APICO genes for T. gondii and to end-point PCR targeting NC5 gene for N. caninum. Thirty-seven out of the one hundred and fifty-nine analyzed samples tested positive for T. gondii with a prevalence of 23.27% and nine for N. caninum, with a prevalence of 5.66%. Thirty-two sequences were obtained from the thirty-seven isolates of T. gondii. Among these, 26 presented alleles compatible with type I strain in 1 or more loci, 4 with type II strain and 2 consisted of atypical strains. Toxoplasma gondii genetic variability in birds of prey confirms previous findings of wildlife as reservoirs of atypical strains. Results from the histology showed few protozoal tissue cysts in skeletal muscle (n. 4) and hearts (n. 2).

Estimating the onset of natal dispersal for a large diurnal raptor: A methodological comparison

We estimated the onset of natal dispersal for a large diurnal raptor with high propensity towards large-scaled exploratory movements during the post-fledging period, the White-tailed Sea Eagle (Haliaeetus albicilla). We analysed GPS tracking data of 21 juveniles with respect to the onset of natal dispersal comparing six methods available from the recent literature. While none of the methods significantly differed from the visual method, the Distance Threshold method underestimated the dispersal onset for some individuals. Likewise, coefficient of variation methods overestimated the dispersal onset in few cases, presumably because the temporal scale of available GPS fixes did not correspond to the scale of discrete dispersal movements. We conclude that all tested methods are generally suitable to estimate the dispersal onset, specifically if the research question does not depend on an exact but rather a rough estimate. A visual determination might increase flexibility to account for individual behavior and yields consistent results across individuals, but highly reduces the comparability across observers and studies. For research questions relying on exact estimates, we propose using a combination of an automated method and a visual determination as a back-up method for single individuals with clear under- or overestimation. An exploratory comparison showed that the temporal resolution of the GPS may further affect the accuracy of natal dispersal estimates. For individuals with clear movement patterns, high-resolution movement data could increase the accuracy of Coefficient of Variation methods. We underline the necessity for further investigation on the effects of temporal resolution on dispersal onset estimates.

Hacking techniques improve health and nutritional status of nestling White-tailed Eagles.

Birds of prey frequently feature in reintroductions and the hacking technique is typically used. Hacking involves removing large nestlings from donor populations, transferring them to captivity, feeding them ad libitum. Potentially, via the hacking method, the stress of captivity and disruption of parental feeding may be detrimental. Alternatively, the provision of ad libitum food may be advantageous. Although hacking has underpinned reintroduction project successes there has been no research on how the method may affect the health and nutritional status of translocated birds during captivity. We compared blood chemistry data from 55 young White-tailed Eagles, translocated from Norway as part of the species' reintroduction to Scotland, from sampling soon after arriving in captivity and again (≈42 days later) before their release. Numerous significant differences between the first and second samples were found, but no significant interactions showed that the sexes responded similarly to captivity. According to hematological and biochemical metrics, individuals showed several changes during captivity, including in red blood cell parameters, plasma proteins, and white cellular parameters related to the immune system, that indicated improved health status. Captivity with ad libitum food was associated with decreased urea and uric acid values: high values can indicate nutritional stress. Urea values became more normally distributed before release, indicating that ad libitum food had reduced nutritional differences between early nestlings in the season and later ones. Despite plentiful food, both sexes lost body mass before release, suggesting an inherent physiological mechanism to improve flight performance in fledglings. We conclude that hacking improved the health and nutritional status of released eagles which is likely to enable birds to cope with greater costs of exploratory behavior which they may require in reintroduction projects. In this context, we note the absence of survival differences between hacked and wild raptors in previous research.

Diversity of diurnal raptors in a suburban area of a city in southern Chile

Raptor conservation programs should be based on knowledge of the birds’ ecology in both natural and urban habitats, justifying the inclusion of ecological studies in suburban zones into regional planning initiatives. The objective of this study was to determine the use of diurnal raptors within the habitats of a suburban area of a city in southern Chile. We characterize the different zones into five types of environment, and assess their raptor diversity for consideration in territorial planning. Acoustic surveys were conducted in auditory stations in addition to observations from fixed transects and trails. From a total of 161.39 h of survey, we obtained 664 sightings corresponding to ten species of diurnal raptors. The richest environment was dense forest (eight species), followed by grassland (six species), native forest regeneration (five species), shrubs (four species) and exotic tree plantations (three species). We discuss the relationship between the richness of diurnal raptors, the types of environment in the study area, and the spatial location of the sites, as well as the implications for territorial planning to support the conservation of birds of prey in the suburban zone studied.

Comparison of blood biochemical parameters of four species of vultures.

Vultures play a very important role in ecosystems by feeding on dead animals and preventing the spread of pathogens. In the mid-20th century in Bulgaria, all species of vultures experienced a rapid population decline and conservation measures include captive breeding and release via adaptation aviaries. Knowledge of the baseline blood biochemical parameters is crucial for the care, rehabilitation and prior to the release of endangered birds of prey. Plasma levels provide valuable information for the evaluation of the physical condition of animals. Between 2020 and 2022, we took blood samples from captive Bearded, Griffon, Cinereous and Egyptian Vultures in Bulgaria (n = 118). We determined the values of 18 parameters - alanine transaminase, albumin, alkaline phosphatase, amylase, aspartate transaminase, calcium, chloride, cholesterol, creatine kinase, creatinine, glucose, lactate dehydrogenase, magnesium, phosphorus, total bilirubin, total protein, triglycerides and uric acid. This research determined the mean blood biochemical indices for aviary Bearded, Griffon, Cinereous and Egyptian Vultures in Bulgaria and compared the values amongst the four vulture species, to serve in determining clinical pathology and nutrition for scavenger birds of different species, age groups and genders in the country. The results of this study suggested that there are significant differences between many of the indicators of the four vulture species. There are fewer differences in the indicators of different ages of birds of a given species and almost no differences are found between the two sexes of a species. These values could be used by scientists, veterinary pathologists, wildlife rehabilitation centres and other researchers. Furthermore, the use of such parameters in assessing population health may enable conservationists to further research environmental conditions affecting the vultures' reproduction and survival.

Allometry of the pectoral flight muscles in birds: Flight style is related to variability in the mass of the supracoracoideus muscle

AbstractAvian flight is powered by a downstroke force generated by the pectoralis (P) muscle and an upstroke force generated by the supracoracoideus (SC) muscle. Some taxa, notably penguins and hummingbirds, have very low P:SC ratios associated with larger masses of the supracoracoideus. Allometric relationships of these muscles are not reported relative to body mass and presumably the two muscles will exhibit isometry in volant birds. This study collated muscle masses for over 600 species representing 28 orders of birds and used phylogenetically controlled analysis of covariance to test for the effects of taxonomic grouping on the allometry of the flight muscles in birds. The P:SC ratio and the standardized residuals for the allometric relationships, were calculated for different orders. The pectoralis scaled isometrically with body mass but the supracoracoideus muscle exhibited a slight but significant negative allometry. Both muscles showed significant effects of taxonomic group but this effect was magnified for the supracoracoideus. Wing‐propelled divers and hovering hummingbirds had disproportionately high proportions of supracoracoideus muscles but tinamous, gamebirds and pigeons, which exhibit burst flight, also had low P:SC ratios. Many taxonomic groups had a ratio around 10:1 but values of 20:1, recorded for birds of prey and owls, were associated with relatively small masses of the supracoracoideus muscle. The P:SC ratio seems to reflect differing flight styles with the greater variability being more associated with the size of the supracoracoideus, the significance of which has not necessarily been fully appreciated in the morphology and flight action of birds.

OUTCOMES OF TREATMENT OF SNAKE AND SCORPION ENVENOMATION IN BIRDS OF PREY, WITH AND WITHOUT ANTIVENOM

Birds of prey are vulnerable to envenomation from animals in their natural environment, including scorpions and pit vipers. Severity of clinical effects varies depending on envenomating species, dose of venom injected, and anatomic site of venom inoculation. Fatality from envenomation has been reported, but use of antivenom in birds of prey is rare. Of 18 identified cases involving envenomation in birds of prey, five received antivenom and survived, seven recovered spontaneously or with supportive care only, and six without antivenom treatment died: four bitten by rattlesnakes of genus Crotalus, one by a cottonmouth (water moccasin, Agkistrodon piscivorus), and one by a coral snake (Micrurus fulvius). Illustrative cases include (1) a California condor (Gymnogyps californianus) fatally envenomated by a rattlesnake of genus Crotalus; (2) a red-tailed hawk (Buteo jamaicensis) bitten by a western diamondback rattlesnake (Crotalus atrox) and successfully treated with IV equine whole-immunoglobulin antivenom despite an apparent acute infusion reaction; (3) a northern crested caracara (Caracara cheriway) with neurotoxicity following envenomation by a bark scorpion (Centruroides sculpturatus), successfully treated with IV equine F(ab')2 antivenom; and (4) a barn owl (Tyto alba) presumed stung by a bark scorpion, with diagnosis proved by specific enzyme-linked immunosorbent assay (ELISA), successfully treated with intramuscular equine F(ab')2 antivenom. Supportive care for envenomation includes oxygen supplementation, maintenance of airway, analgesics, and fluid therapy. Antivenom may be useful, and its use should be considered for symptomatic envenomation. Additional considerations in the context of antivenom use include dose, route of administration, volume, readiness of antihistamines and epinephrine for treatment of possible adverse events, and consultation with a medical toxinologist.

Breeding performance is explained for coloniality and phenology but not for urbanization in a generalist raptor bird

Breeding performance is explained for coloniality and phenology but not for urbanization in a generalist raptor bird

Законодательная охрана хищных птиц и усиление борьбы с нелегальной торговлей ими в Казахстане

Законодательная охрана хищных птиц и усиление борьбы с нелегальной торговлей ими в Казахстане

Хищные птицы и ветроэнергетика в Казахстане: какие перспективы для орлов?

Хищные птицы и ветроэнергетика в Казахстане: какие перспективы для орлов?