The use of social information in vulture flight decisions.

Animals rely on a balance of personal and social information to decide when and where to move next in order to access a desired resource. The benefits from cueing on conspecifics to reduce uncertainty about resource availability can be rapidly overcome by the risks of within-group competition, often exacerbated toward low-ranked individuals. Being obligate soarers, relying on thermal updraughts to search for carcasses around which competition can be fierce, vultures represent ideal models to investigate the balance between personal and social information during foraging movements. Linking dominance hierarchy, social affinities and meteorological conditions to movement decisions of eight captive vultures, Gyps spp., released for free flights in natural soaring conditions, we found that they relied on social information (i.e. other vultures using/having used the thermals) to find the next thermal updraught, especially in unfavourable flight conditions. Low-ranked individuals were more likely to disregard social cues when deciding where to go next, possibly to minimize the competitive risk of social aggregation. These results exemplify the architecture of decision-making during flight in social birds. It suggests that the environmental context, the context of risk and the social system as a whole calibrate the balance between personal and social information use.

Spillover of Newcastle disease virus to Himalayan Griffon vulture: a possible food-based transmission.

The Newcastle disease virus (NDV) affects wild and domesticated bird species, including commercial poultry. Although the diversity of NDV in domestic chickens is well documented, limited information is available about Newcastle disease (ND) outbreaks in other bird species. We report an annotated sequence of NDV/Vulture/Borjuri/01/22, an avirulent strain of NDV reported from Borjuri, Northeast India, in Himalayan Griffon vulture. The complete genome is 15,186 bases long with a fusion protein (F) cleavage site 112GRQGR↓L117. The phylogenetic analysis based on the F protein gene and the whole genome sequence revealed that the isolate from the vulture belongs to genotype II, sharing significant homology with vaccine strain LaSota. The study highlights the possible spillover of the virus from domestic to wild species through the food chain.

Blood lead levels in an endangered vulture decline following changes in hunting activity.

Lead ammunition stands out as one of the most pervasive pollutants affecting wildlife. Its impact on bird populations have spurred efforts for the phase-out of leaded gunshot in several countries, although with varying scopes and applications. Ongoing and future policy changes require data to assess the effectiveness of adopted measures, particularly in the current context of biodiversity loss. Here, we assessed the long-term changes in blood lead (Pb) levels of Egyptian vultures from the Canary Islands, Spain, which have been severely affected by Pb poisoning over the past two decades. During this period, the reduction in hunting pressure and changes in legislation regarding firearms usage for small game hunting likely contributed to a decrease in environmental Pb availability. As anticipated, our results show a reduction in Pb levels, especially after the ban on wild rabbit hunting with shotgun since 2010. This effect was stronger in the preadult fraction of the vulture population. However, we still observed elevated blood Pb levels above the background and clinical thresholds in 5.6% and 1.5% of individuals, respectively. Our results highlight the positive impact of reducing the availability of Pb from ammunition sources on individual health. Nonetheless, the continued use of Pb gunshot remains an important source of poisoning, even lethal, mainly affecting adult individuals. This poses a particular concern for long-lived birds, compounding by potential chronic effects associated with Pb bioaccumulation. Our findings align with recent studies indicating insufficient reductions in Pb levels among European birds of prey, attributed to limited policy changes and their uneven implementation. We anticipated further reductions in Pb levels among Egyptian vultures with expanded restrictions on hunting practices, including a blanket ban on Pb shot usage across all small game species.

Time constraints may pace the ontogeny of movement behaviour.

During early development, juvenile animals need to acquire a diverse behavioural repertoire to interact with their environment. The ontogeny of animal behaviour, is paced by the motivation to improve, e.g. internal clocks, and limited by external constraints, e.g. weather conditions. We here evaluate how naive Egyptian vultures (Neophron percnopterus) improve in locomotor performance, measured as daily maximum displacement, prior to their first migration under three different time constraint regimes: we compared wild hatched vultures, migrating one month after fledging, with captive-hatched vultures, released in spring four months or in winter nine months before migration. We found that the time until migration paced the development of movement behaviour: wild birds rapidly increased displacement distances within the first two weeks after fledging, while spring and winter released vultures delayed movement increases by two and four months, respectively. Under relaxed time constraints captive-hatched vultures displayed diverse functional forms of performance enhancements and therefore great variability in individual ontogeny of movement behaviour. While weather conditions in winter could limit flight movements, some birds indeed moved immediately after their release, indicating that weather may not be limiting. Our findings promote the idea that relaxed ecological constraints could uncover hidden phenotypic flexibility in ontogeny, which could present a greater potential for adaptability under environmental change than currently expected.

A utilization distribution for the global population of Cape Vultures (Gyps coprotheres) to guide wind energy development.

The rapid development of wind energy in southern Africa represents an additional threat to the already fragile populations of African vultures. The distribution of the vulnerable Cape Vulture Gyps coprotheres overlaps considerably with wind energy development areas in South Africa, creating conflicts that can hinder both vulture conservation and sustainable energy development. To help address this conflict and aid in the safe placement of wind energy facilities, we map the utilization distribution (UD) of this species across its distributional range. Using tracking data from 68 Cape Vultures collected over the last 20 years, we develop a spatially explicit habitat use model to estimate the expected UDs around known colonies. Scaling the UDs by the number of vultures expected to use each of the colonies, we estimate the Cape Vulture population utilization distribution (PUD) and determine its exposure to wind farm impacts. To complement our results, we model the probability of a vulture flying within the rotor sweep area of a wind turbine throughout the species range and use this to identify areas that are particularly prone to collisions. Overall, our estimated PUD correlates well with reporting rates of the species from the Southern African Bird Atlas Project, currently used to assess potential overlap between Cape Vultures and wind energy developments, but it adds important benefits, such as providing a spatial gradient of activity estimates over the entire species range. We illustrate the application of our maps by analyzing the exposure of Cape Vultures in the Renewable Energy Development Zones (REDZs) in South Africa. This application is a scalable procedure that can be applied at different planning phases, from strategic, nationwide planning to project-level assessments.

Value of combining transect counts and telemetry data to determine short-term population trends in a globally threatened species.

To evaluate conservation interventions, it is necessary to obtain reliable population trends for short (<10 years) time scales. Telemetry can be used to estimate short-term survival rates and is a common tool for assessing population trends, but it has limitations and can be biased toward specific behavioral traits of tagged individuals. Encounter rates calculated from transects can be useful for assessing changes across multiple species, but they can have large confidence intervals and be affected by variations in survey conditions. The decline of African vultures has been well-documented, but understanding of recent trends is lacking. To examine population trends, we used survival estimates from telemetry data collected over 6 years (primarily for white-backed vultures [Gyps africanus]) and transect counts conducted over 8 years (for 7 scavenging raptors) in 3 large protected areas in Tanzania. Population trends were estimated using survival analysis combined with the Leslie Lefkovitch matrix model from the telemetry data and using Bayesian mixed effects generalized linear regression models from the transect data. Both methods showed significant declines for white-backed vultures in Ruaha and Nyerere National Parks. Only telemetry estimates suggested significant declines in Katavi National Park. Encounter rates calculated from transects also showed declines in Nyerere National Park for lappet-faced vultures (38% annual declines) and Bateleurs (18%) and in Ruaha National Park for white-headed vultures (Trigonoceps occipitalis) (19%). Mortality rates recorded and inferred from telemetry suggested that poisoning is prevalent. However, only 6 mortalities of the 26 presumed mortalities were confirmed to be caused by poisoning, highlighting the challenges of determining the cause of death when working across large landscapes. Despite declines, our data provide evidence that southern Tanzania has higher current encounter rates of African vultures than elsewhere in East Africa. Preventing further declines will depend greatly on mitigating poisoning. Based on our results, we suggest that the use of multiple techniques improves understanding of population trends over the short term.

Importancia de combinar los conteos de transectos y los datos de telemetría para determinar las tendencias poblacionales a corto plazo de especies amenazadas a nivel mundial Resumen Para evaluar las intervenciones de conservación es necesario obtener tendencias poblacionales confiables para escalas temporales cortas (<10 años). La telemetría puede usarse para estimar las tasas de supervivencia a corto plazo, además de que es una herramienta común para analizar las tendencias poblacionales, pero tiene limitantes y puede sesgarse con el comportamiento específico de los individuos marcados. Las tasas de encuentro calculadas a partir de transectos pueden ser útiles para analizar cambios en varias especies, aunque pueden tener intervalos grandes de confianza y verse afectadas por las variantes en las condiciones del censo. La declinación de los buitres africanos está bien documentada, pero hace falta el conocimiento sobre las tendencias recientes. Usamos las estimaciones de supervivencia tomadas de datos telemétricos recolectados durante seis años (principalmente del buitre Gyps africanus) y los conteos de transecto de siete especies carroñeras realizados durante ocho años en tres áreas protegidas en Tanzania. Estimamos las tendencias poblacionales con la combinación de análisis de supervivencia y el modelo de matriz Leslie Lefkovitch hecho con los datos telemétricos y usando modelos bayesianos de regresión lineal generalizada de efectos mixtos hechos con los datos de los transectos. Ambos métodos indicaron declinaciones significativas de Gyps africanus en los Parques Nacionales Ruaha y Nyerere. Sólo las estimaciones telemétricas sugirieron una declinación significativa en el Parque Nacional Katavi. Las tasas de encuentro calculadas a partir de los transectos también indicaron declinaciones de Torgos tracheliotos (38% de declinaciones anuales) y de Terathopius ecaudutus (18%) en el Parque Nacional Nyerere y de Trigonoceps occipitalis (19%) en el Parque Nacional Ruaha. Las muertes registradas e inferidas a partir de la telemetría sugieren que el envenenamiento es prevalente. Sin embargo, sólo se confirmaron seis muertes por envenenamiento de las 26 supuestas, lo que resalta los obstáculos para determinar la causa de muerte cuando se trabaja en paisajes amplios. A pesar de las declinaciones, nuestros datos proporcionan evidencia de que el sur de Tanzania tiene tasas actuales de encuentro con buitres africanos más altas que en cualquier otra parte del occidente de África. La prevención de declinaciones en el futuro dependerá principalmente de evitar el envenenamiento. Con base en nuestros resultados, sugerimos que el uso de técnicas múltiples incrementa el conocimiento sobre las tendencias poblacionales a corto plazo.

Optimized Back Propagation Neural Network Using Quasi-Oppositional Learning-Based African Vulture Optimization Algorithm for Data Fusion in Wireless Sensor Networks.

A Wireless Sensor Network (WSN) is a group of autonomous sensors geographically distributed for environmental monitoring and tracking purposes. Since the sensors in the WSN have limited battery capacity, the energy efficiency is considered a challenging task because of redundant data transmission and inappropriate routing paths. In this research, a Quasi-Oppositional Learning (QOL)-based African Vulture Optimization Algorithm (AVOA), referred to as QAVOA, is proposed for an effective data fusion and cluster-based routing in a WSN. The QAVOA-based Back Propagation Neural Network (BPNN) is developed to optimize the weights and threshold coefficients for removing the redundant information and decreasing the amount of transmitted data over the network. Moreover, the QAVOA-based optimal Cluster Head Node (CHN) selection and route discovery are carried out for performing reliable data transmission. An elimination of redundant data during data fusion and optimum shortest path discovery using the proposed QAVOA-BPNN is used to minimize the energy usage of the nodes, which helps to increase the life expectancy. The QAVOA-BPNN is analyzed by using the energy consumption, life expectancy, throughput, End to End Delay (EED), Packet Delivery Ratio (PDR) and Packet Loss Ratio (PLR). The existing approaches such as Cross-Layer-based Harris-Hawks-Optimization (CL-HHO) and Improved Sparrow Search using Differential Evolution (ISSDE) are used to evaluate the QAVOA-BPNN method. The life expectancy of QAVOA-BPNN for 500 nodes is 4820 rounds, which is high when compared to the CL-HHO and ISSDE.

Vulture Genomes Reveal Molecular Adaptations Underlying Obligate Scavenging and Low Levels of Genetic Diversity.

Obligate scavenging on the dead and decaying animal matter is a rare dietary specialization that in extant vertebrates is restricted to vultures. These birds perform essential ecological services, yet many vulture species have undergone recent steep population declines and are now endangered. To test for molecular adaptations underlying obligate scavenging in vultures, and to assess whether genomic features might have contributed to their population declines, we generated high-quality genomes of the Himalayan and bearded vultures, representing both independent origins of scavenging within the Accipitridae, alongside a sister taxon, the upland buzzard. By comparing our data to published sequences from other birds, we show that the evolution of obligate scavenging in vultures has been accompanied by widespread positive selection acting on genes underlying gastric acid production, and immunity. Moreover, we find evidence of parallel molecular evolution, with amino acid replacements shared among divergent lineages of these scavengers. Our genome-wide screens also reveal that both the Himalayan and bearded vultures exhibit low levels of genetic diversity, equating to around a half of the mean genetic diversity of other bird genomes examined. However, demographic reconstructions indicate that population declines began at around the Last Glacial Maximum, predating the well-documented dramatic declines of the past three decades. Taken together, our genomic analyses imply that vultures harbor unique adaptations for processing carrion, but that modern populations are genetically depauperate and thus especially vulnerable to further genetic erosion through anthropogenic activities.

An Improved African Vulture Optimization Algorithm for Dual-Resource Constrained Multi-Objective Flexible Job Shop Scheduling Problems.

According to the characteristics of flexible job shop scheduling problems, a dual-resource constrained flexible job shop scheduling problem (DRCFJSP) model with machine and worker constraints is constructed such that the makespan and total delay are minimized. An improved African vulture optimization algorithm (IAVOA) is developed to solve the presented problem. A three-segment representation is proposed to code the problem, including the operation sequence, machine allocation, and worker selection. In addition, the African vulture optimization algorithm (AVOA) is improved in three aspects: First, in order to enhance the quality of the initial population, three types of rules are employed in population initialization. Second, a memory bank is constructed to retain the optimal individuals in each iteration to increase the calculation precision. Finally, a neighborhood search operation is designed for individuals with certain conditions such that the makespan and total delay are further optimized. The simulation results indicate that the qualities of the solutions obtained by the developed approach are superior to those of the existing approaches.

Correlation between wing bone microstructure and different flight styles: The case of the griffon vulture (gyps fulvus) and greater flamingo (phoenicopterus roseus).

Flying is the main means of locomotion for most avian species, and it requires a series of adaptations of the skeleton and of feather distribution on the wing. Flight type is directly associated with the mechanical constraints during flight, which condition both the morphology and microscopic structure of the bones. Three primary flight styles are adopted by avian species: flapping, gliding, and soaring, with different loads among the main wing bones. The purpose of this study was to evaluate the cross-sectional microstructure of the most important skeletal wing bones, humerus, radius, ulna, and carpometacarpus, in griffon vultures (Gyps fulvus) and greater flamingos (Phoenicopterus roseus). These two species show a flapping and soaring flight style, respectively. Densitometry, morphology, and laminarity index were assessed from the main bones of the wing of 10 griffon vultures and 10 flamingos. Regarding bone mineral content, griffon vultures generally displayed a higher mineral density than flamingos. Regarding the morphology of the crucial wing bones involved in flight, while a very slightly longer humerus was observed in the radius and ulna of flamingos, the ulna in griffons was clearly longer than other bones. The laminarity index was significantly higher in griffons. The results of the present study highlight how the mechanics of different types of flight may affect the biomechanical properties of the wing bones most engaged during flight.

Differential survival throughout the full annual cycle of a migratory bird presents a life-history trade-off.

Long-distance migrations are among the most physically demanding feats animals perform. Understanding the potential costs and benefits of such behaviour is a fundamental question in ecology and evolution. A hypothetical cost of migration should be outweighed by higher productivity and/or higher annual survival, but few studies on migratory species have been able to directly quantify patterns of survival throughout the full annual cycle and across the majority of a species' range. Here, we use telemetry data from 220 migratory Egyptian vultures Neophron percnopterus, tracked for 3,186 bird months and across approximately 70% of the species' global distribution, to test for differences in survival throughout the annual cycle. We estimated monthly survival probability relative to migration and latitude using a multi-event capture-recapture model in a Bayesian framework that accounted for age, origin, subpopulation and the uncertainty of classifying fates from tracking data. We found lower survival during migration compared to stationary periods (ß = -0.816; 95% credible interval: -1.290 to -0.318) and higher survival on non-breeding grounds at southern latitudes (<25°N; ß = 0.664; 0.076-1.319) compared to on breeding grounds. Survival was also higher for individuals originating from Western Europe (ß = 0.664; 0.110-1.330) as compared to further east in Europe and Asia, and improved with age (ß = 0.030; 0.020-0.042). Anthropogenic mortalities accounted for half of the mortalities with a known cause and occurred mainly in northern latitudes. Many juveniles drowned in the Mediterranean Sea on their first autumn migration while there were few confirmed mortalities in the Sahara Desert, indicating that migration barriers are likely species-specific. Our study advances the understanding of important fitness trade-offs associated with long-distance migration. We conclude that there is lower survival associated with migration, but that this may be offset by higher non-breeding survival at lower latitudes. We found more human-caused mortality farther north, and suggest that increasing anthropogenic mortality could disrupt the delicate migration trade-off balance. Research to investigate further potential benefits of migration (e.g. differential productivity across latitudes) could clarify how migration evolved and how migrants may persist in a rapidly changing world.

Limited sexual segregation in a dimorphic avian scavenger, the Andean condor.

Sexual segregation is widely reported among sexually dimorphic species and generally attributed to intraspecific competition. Prey diversity and human activities can reinforce niche segregation by increasing resource heterogeneity. Here, we explored trophic and spatial sexual segregation in the only avian scavenger that exhibits pronounced sexual size dimorphism (up to 50% difference in body mass) and a highly despotic social system, the Andean condor (Vultur gryphus). We predicted that larger and dominant males would exclude smaller and subordinate females from high-quality resources, leading to sexual segregation particularly in human-dominated landscapes showing increased prey diversity. We compared resource use between females and males across six sites in Argentina featuring a range of prey diversity via stable isotopes analysis of molted feathers (n = 141 individuals). We then focused on two sites featuring contrasting levels of prey diversity and quantified assimilated diet via stable isotopes and space use via GPS monitoring (n = 23 and 12 tagged individuals). We found no clear differences in isotopic niche space, individual variation in isotopic signature, or assimilated diet between females and males. However, there were differences in foraging locations between sexes, with females apparently using areas of fewer food resources more frequently than males. Local conditions defined the dynamics of fine-scale sexual differences in foraging sites; yet, unpredictable and ephemeral carrion resources likely prevent segregation by sexes at the landscape scale. Our study highlights complex dynamics of sexual segregation in vultures and the relevancy of analyses under multiple spatial-temporal scales to explore segregation in social species.

Emerging Pathogenic Gammaproteobacteria Wohlfahrtiimonas chitiniclastica and Ignatzschineria Species in a Turkey Vulture (Cathartes aura).

New World vultures, such as turkey vultures (Cathartes aura), are obligate scavengers with large geographic ranges. In a preliminary characterization of the turkey vulture (TV) gastrointestinal microbiome in Southern California, we identified 2 recently described emerging bacterial pathogens not previously known to be associated with this avian species. High-throughput sequencing of broad-range 16S rRNA gene amplicons revealed sequences from TV cloacal swabs that were related closest to Wohlfahrtiimonas chitiniclastica and Ignatzschineria species, both Gammaproteobacteria considered by the United States Centers for Disease Control and Prevention as emerging zoonotic pathogens. None of these bacterial sequence types have been previously identified from samples obtained from the turkey vulture gastrointestinal microbiome. With the use of bioinformatics workflows previously established by our research group, we designed specific and sensitive polymerase chain reaction primer sets that represent novel diagnostic assays for the genera Wohlfahrtiimonas and Ignatzschineria. These primer sets were validated by Sanger sequence confirmation from complex TV samples. Because the genera Wohlfahrtiimonas and Ignatzschineria are both known to have dipteran hosts, the molecular diagnostic tools we present here should be useful for better understanding the role of flies, vultures, and other scavengers in the ecology and epidemiology of the genera Wohlfahrtiimonas and Ignatzschineria from a One Health perspective.

Too much is bad: increasing numbers of livestock and conspecifics reduce body mass in an avian scavenger.

Individual traits such as body mass can serve as early warning signals of changes in the fitness prospects of animal populations facing environmental impacts. Here, taking advantage of a 19-yr monitoring, we assessed how individual, population, and environmental factors modulate long-term changes in the body mass of Canarian Egyptian vultures. Individual vulture body mass increased when primary productivity was highly variable, but decreased in years with a high abundance of livestock. We hypothesized that carcasses of wild animals, a natural food resource that can be essential for avian scavengers, could be more abundant in periods of weather instability but depleted when high livestock numbers lead to overgrazing. In addition, increasing vulture population numbers also negatively affect body mass suggesting density-dependent competition for food. Interestingly, the relative strength of individual, population and resource availability factors on body mass changed with age and territorial status, a pattern presumably shaped by differences in competitive abilities and/or age-dependent environmental knowledge and foraging skills. Our study supports that individual plastic traits may be extremely reliable tools to better understand the response of secondary consumers to current and future natural and human-induced environmental changes.

Ophthalmic findings in cinereous vultures (Aegypius monachus).

OBJECTIVE: The aim of the present study was to provide ophthalmic reference values under normal physiological conditions for Aegypius monachus (cinereous vulture). PROCEDURES: Thirty-two eyes of sixteen adult captive cinereous vultures were used for this study. Tear tests and tonometry in conscious and anesthetized states, neuro-ophthalmic tests, measurement of corneal diameter, slit-lamp biomicroscopy, ophthalmoscopy, and funduscopy were performed. RESULTS: Schirmer tear test (STT) value was 11.4 ± 2.6 and 11.5 ± 2.8 mm/min in the right (OD) and left eye (OS), respectively. Phenol red thread test (PRT) values were 22.3 ± 2.1 mm/15 s OD and 22.8 ± 3.0 mm/15 s OS. The results showed a strong correlation between STT and PRT in both eyes. Intraocular pressure (IOP) values were 32.8 ± 6.9 mm Hg OD and 31.9 ± 7.1 mm Hg OS with TonoVet and 20.7 ± 4.5 mm Hg OD and 19.5 ± 4.1 mm Hg OS with Tono-Pen. There were significant differences in IOPs between rebound and applanation tonometry in both OD and OS. Tear production and IOP values showed significant reductions with general anesthesia in both tear tests and both tonometry (P < .001). Horizontal corneal diameter (mm) was 15.56 ± 0.96 OD and 15.56 ± 0.96 OS. Vertical diameter (mm) was 14.13 ± 0.96 OD and 14.06 ± 1.06 OS. The horizontal diameter was significantly longer than vertical diameter (P < .001). CONCLUSIONS: Ocular morphologic information and normal reference range values for various ophthalmic measurements were obtained in clinically healthy cinereous vultures, which can facilitate accurate diagnosis and better management of ophthalmic diseases in cinereous vultures.

The mesoscavenger release hypothesis and implications for ecosystem and human well-being.

Many apex scavenger species, including nearly all obligate scavengers, are in a state of rapid decline and there is growing evidence these declines can drastically alter ecological food webs. Our understanding of how apex scavengers regulate populations of mesoscavengers, those less-efficient scavengers occupying mid-trophic levels, is improving; yet, there has been no comprehensive evaluation of the evidence around the competitive release of these species by the loss of apex scavengers. Here we present current evidence that supports the mesoscavenger release hypothesis, the increase in mesoscavengers and increase in carrion in the face of declining apex scavengers. We provide two models of scavenger dynamics to demonstrate that the mesoscavenger release hypothesis is consistent with ecological theory. We further examine the ecological and human well-being implications of apex scavenger decline, including carrion removal and disease regulation services.

Genome-wide analysis reveals the genomic features of the turkey vulture (Cathartes aura) as a scavenger.

Cathartidae is a small family of large-bodied carrion-feeding birds, of which the turkey vulture (Cathartes aura, Cathartidae) is the most widespread distributed. To investigate the chemoreception system, detoxification system, and immune system in the turkey vulture, we compared its genome to 14 other avian genomes. Comparative genomics demonstrated the expansion in the chemoreception system, especially the olfactory receptors, while the genes in the detoxification system of the turkey vulture did not show apparent expansion. We identified five positively selected genes associated with the immune system in the turkey vulture, which was likely to strengthen the immune defense against pathogenic invasion. Functional enrichment analysis indicated that many positively selected genes were involved in the regulation of immune system processes, implying important reorganization of the immune system in the turkey vulture. The turkey vulture-specific missense mutations were found in one positively selected gene (BCL6), and all the missense mutations were classified as deleterious by PolyPhen-2, possibly contributing to immune adaptation to the carrion feeding. Furthermore, we identified four turkey vulture-specific missense mutations in three ß-defensin genes of the turkey vulture, which was an indispensable part in the innate immunity (a natural barrier against invasive microbes including bacteria, fungi, and viruses). Our genomic analyses in the turkey vulture provided insights into the genetic signatures of the adaptation to the carrion feeding.

Sight or smell: which senses do scavenging raptors use to find food?

Raptors are usually considered to be mainly visually dependent, and the use of other sensory modalities has rarely been studied in these birds. Here, we investigated experimentally which senses (vision and/or olfaction) Turkey vultures (Cathartes aura) and Southern caracaras (Caracara plancus) use to find hidden food. First, two identical stainless-steel perforated balls, one containing a putrefied piece of meat and the other an odorless control, were presented to birds in binary choice experiments. Both species interacted more with the smelling ball than with the control, suggesting that they were attracted by the odor of the hidden meat. In a second experiment, individuals were accustomed to eat in one specifically colored ball (blue or green). In the test phase, the meat was hidden in the opposite color with respect to the one each bird had become accustomed to. Vultures still interacted more with the smelly ball disregarding the color, while caracaras interacted equally with the two balls. The prevalence of olfaction in Turkey vultures may partly explain why they are the first raptors to find carcasses in tropical forests. In contrast, caracaras forage on the ground opportunistically, a strategy where both olfaction and sight may be involved. Our experiments suggest that both species are able to use olfactory cues for foraging. However, olfaction could be the predominant sense in Turkey vultures while olfaction and sight could play an equivalent role in Southern caracaras.

Simultaneous-count models to estimate abundance from counts of unmarked individuals with imperfect detection.

We developed a method to estimate population abundance from simultaneous counts of unmarked individuals over multiple sites. We considered that at each sampling occasion, individuals in a population could be detected at 1 of the survey sites or remain undetected and used either multinomial or binomial simultaneous-count models to estimate abundance, the latter being equivalent to an N-mixture model with one site. We tested model performance with simulations over a range of detection probabilities, population sizes, growth rates, number of years, sampling occasions, and sites. We then applied our method to 3 critically endangered vulture species in Cambodia to demonstrate the real-world applicability of the model and to provide the first abundance estimates for these species in Cambodia. Our new approach works best when existing methods are expected to perform poorly (i.e., few sites and large variation in abundance among sites) and if individuals may move among sites between sampling occasions. The approach performed better when there were >8 sampling occasions and net probability of detection was high (>0.5). We believe our approach will be useful in particular for simultaneous surveys at aggregation sites, such as roosts. The method complements existing approaches for estimating abundance of unmarked individuals and is the first method designed specifically for simultaneous counts.

Modelos de Conteo Simultáneo para Estimar la Abundancia a partir de Conteos de Individuos No Marcados con Detección Imperfecta Resumen Desarrollamos un método para estimar la abundancia poblacional a partir de conteos simultáneos de individuos sin marcaje en múltiples sitios. Consideramos que en cada ocasión de muestreo los individuos de una población podrían ser detectados en uno de los sitios de censos o podrían permanecer sin ser detectados y usamos modelos de conteo simultáneo multinomial o binomial para estimar la abundancia, con el binomial como equivalente a un modelo de mezcla N con un solo sitio. Probamos el desempeño del modelo con simulaciones en un rango de probabilidades de detección, tamaños poblacionales, tasas de crecimiento, número de años, ocasiones de muestreo, y sitios. Después aplicamos nuestro método a tres especies de buitre que se encuentran en peligro crítico en Camboya para demostrar cuán aplicable es el modelo en el mundo real y para proporcionar las primeras estimaciones de abundancia para estas especies en Camboya. Nuestra nueva estrategia trabaja de mejor manera cuando se espera que los modelos existentes tengan un desempeño pobre (es decir, pocos sitios y una gran variación en la abundancia entre sitios) y si los individuos podrían moverse de un sitio a otro entre cada ocasión de muestreo. La estrategia tuvo un mejor desempeñó cuando hubo >8 ocasiones de muestreo y la probabilidad neta de detección fue alta (>0.5). Creemos que nuestra estrategia será especialmente útil para censos simultáneos en sitios de agregación, como los nidos. El método complementa las estrategias existentes para estimar la abundancia de individuos sin marcaje y es el primer método diseñado específicamente para conteos simultáneos.

Vultures respond to challenges of near-ground thermal soaring by varying bank angle.

Many large birds rely on thermal soaring flight to travel cross-country. As such, they are under selective pressure to minimise the time spent gaining altitude in thermal updrafts. Birds should be able to maximise their climb rates by maintaining a position close to the thermal core through careful selection of bank angle and airspeed; however, there have been few direct measurements of either parameter. Here, we apply a novel methodology to quantify the bank angles selected by soaring birds using on-board magnetometers. We couple these data with airspeed measurements to parameterise the soaring envelope of two species of Gyps vulture, from which it is possible to predict 'optimal' bank angles. Our results show that these large birds respond to the challenges of gaining altitude in the initial phase of the climb, where thermal updrafts are weak and narrow, by adopting relatively high, and conserved, bank angles (25-35 deg). The bank angle decreased with increasing altitude, in a manner that was broadly consistent with a strategy of maximising the rate of climb. However, the lift coefficients estimated in our study were lower than those predicted by theoretical models and wind-tunnel studies. Overall, our results highlight how the relevant currency for soaring performance changes within individual climbs: when thermal radius is limiting, birds vary bank angle and maintain a constant airspeed, but speed increases later in the climb in order to respond to decreasing air density.