Félix Hernán Vargas

The Journal of Raptor Research publishes the biology and conservation of diurnal and nocturnal raptors, such as their ecology, behavior, and conservation.

Existe escaso conocimiento del águila harpía (Harpia harpyja) en el norte de su distribución, siendo el ave rapaz y depredador tope más raro y amenazado. Aquí documentamos la presencia de un águila harpía inmaduro en Chiapas, México, registrado dentro del marco de un esfuerzo de monitoreo y conservación de rapaces neotropicales en la selva Lacandona, integrado por investigadores y monitores comunitarios. El registro se obtuvo el 12 de junio de 2023 mediante una observación fortuita ocurrida en un claro desmontado al interior de una extensión de selva alta perennifolia en buen estado de conservación. Este registro representa el primer avistamiento de la especie en México, sustentado con evidencia fotográfica y en video en más de una década. La presencia del individuo inmaduro supone la existencia de una pareja reproductiva en la Selva Maya, y resalta la urgente necesidad de fortalecer las estrategias de monitoreo y conservación de la especie y su hábitat.

In raptors, size-related differences between sexes affect the choice of prey. While the broad patterns of the globally endangered black-and-chestnut eagle’s (Spizaetus isidori) feeding habits are known in the northern Andes, specific knowledge of the sex-related diet differences in the species remains unknown. Here, we conducted direct observations to evaluate the differences in prey size between female and male eagles, as well as the numerical rates of prey delivery to nestlings, and the differences in prey diversity between sexes, in nine nests in Ecuador. Males provided more prey to nestlings than females (227 vs. 99 prey items, respectively), and females hunted heavier prey than males (on average 1.19 vs. 0.95 kg, respectively). The overlap in captured prey between sexes was relatively high (O = 0.67), which suggests potential for competition. There was no difference between male and female black-and-chestnut eagles in either prey diversity or the composition of the prey species when considering the main prey items. However, the sexes differed in the prey items at lower biomass contributions. Males’ prey were primarily bird species from the orders Galliformes, Columbiformes, and Psittaciformes, while females’ prey were mostly mammal species from the orders Primates and Carnivora, and some passerine birds. Both sexes preferred arboreal species, but males hunted more scansorial and terrestrial prey. Our data suggest that sex-related differences in the eagle’s dietary contribution to nestlings likely result from parental role differentiation, rather than intersexual competition.

Scientific knowledge of vertebrate scavenging communities has increased over the last decades. However, there is a lack of information on the Neotropics. We aimed to describe the vertebrate scavenger community of the tropical dry forest of western Ecuador and to identify the factors influencing carcass consumption patterns by this guild. Between November 2022 and May 2023, we placed 64 experimental carcasses of different sizes in eight camera-trapping stations (32 carcasses for each category). At each station, we simultaneously placed two carcasses at least 100 m apart: one small-sized (chicken) and one medium-sized (goats or pigs) carcass. We fitted Generalized Linear Mixed Models to assess the effects of carcass size and season (rainy and dry) on the scavenger species richness and abundance, considering all scavenger species and by species group. We also fitted Linear Mixed Models to assess differences in carcass detection time, total consumption time and rate, using the carcass size, vulture abundance, and percentage of canopy cover as predictors. The scavenger community was dominated by obligate scavengers (i.e., vultures), and the species detected were the Black Vulture (Coragyps atratus), the Turkey Vulture (Cathartes aura), and the King Vulture (Sarcoramphus papa). Facultative mammalian scavengers such as Ocelot (Leopardus pardalis), Tayra (Eira barbara), Crab-eating Raccoon (Procyon cancrivorus) and domestic dog (Canis lupus familiaris) were recorded in a smaller number of carcasses. No facultative avian scavenger species were detected. Carcass size influenced all the variables analyzed, except the scavenger species richness. While the season influenced the vulture abundance, especially of S. papa. Facultative scavenger richness and abundance did not show significant differences. Carcass total consumption time was not explained by any of the variables included in the models. Both carcass detection time and consumption rates were influenced by carcass size, particularly in the case of consumption rates, where larger carcasses exhibited higher consumption rates than smaller ones. The dominance of vulture species in the scavenger community suggests that their ecological role is indispensable for the dry forest of western Ecuador. The loss of obligate scavengers could have important implications for ecosystem services and human well-being.

Investigamos el parasitismo de dípteros del género Philornis en los nidos de Rostrhamus sociabilis en campos de arroz y áreas inundadas del oeste de Ecuador durante 2020 y 2021, mediante el análisis de sus nidos después de la salida de los volantones. Los datos morfológicos y moleculares llevaron al descubrimiento de dos especies de moscas Philornis (Diptera: Muscidae) dentro de los nidos de R. sociabilis: P. falsificus y P. downsi. Estos resultados representan los primeros registros de R. sociabilis como especie huésped de cualquier especie de Philornis. La prevalencia de pupas de Philornis en nidos de R. sociabilis fue del 22% y 9.7% durante 2020 y 2021, respectivamente. En 2021, la proporción de nidos que lograron producir al menos un volantón fue del 74%, mientras que el 26% restante de los nidos fracasaron durante la incubación o la fase de cría. La mortalidad de los pollos atribuible al parasitismo de Philornis parece ser baja. También documentamos el parasitismo de P. falsificus por la avispa parasitoide Spalangia sp. (Hymenoptera; Pteromalidae). [Traducción de los autores editada]

Vultures provide the key ecosystem service of quickly removing carrion, so they have recently been assumed to be top scavengers. To challenge the concept of top scavenger (i.e. the most influential in the scavenging community and process), between 2012 and 2019, we recorded the consumption of 45 equine carcasses available for two different avian scavenger guilds in the Tropical Andes; each guild included the Andean Condor, the alleged top scavenger. The carcasses eaten by Andean Condors were consumed, on average, 1.75 times faster than those they did not eat. Furthermore, the greater abundance of feeding condors shortened carcass consumption time more than a greater abundance of any other species by 1.65 to 5.96 times, on average. These findings support the hypothesis that the Andean Condor significantly drives scavenging dynamics and is, therefore, an unrestricted top scavenger. Additionally, we established a gradient of tolerance of avian scavengers to domestic dog disturbance at carcasses, from highest to lowest: vultures > caracaras > condors. Our study framework holds great potential for advancing in food webs’ comprehension through quantifying the relative functional role of scavenging communities’ members and for guiding efforts to weigh up the ecological contributions of top scavengers and foster their conservation.

Background and Research Aims: Native vertebrate scavenger communities may be affected by free-ranging dogs ( Canis lupus familiaris), but little information is available on this subject. We aimed to evaluate the influence of free-ranging dogs on a community of native vertebrate scavengers and to propose management and conservation actions. Methods: Between November 2014 and June 2016, we systematically monitored 37 ungulate carcasses in the buffer zone of Antisana National Park, Andes of Ecuador at an elevation range between 3000 and 4150 m asl. We monitored carcasses with camera traps operating 24 hours per day. Results: We obtained 1010 independent events and recorded seven vertebrate scavenger species. Free-ranging dogs were present at carcasses for 40.39% of the total activity time, but the most frequently recorded species were the Andean fox ( Lycalopex culpaeus) and the Carunculated Caracara ( Phalcoboenus carunculatus). The scavenging birds were diurnal, the Andean fox was mostly nocturnal, and the free-ranging dogs were active in all periods of the day. Native scavenger species changed their peak of activity to times when the free-ranging dogs were less active, probably to avoid agonistic encounters. The presence of free-ranging dogs negatively influenced the number of independent events of the native species. Conclusion: The presence of free-ranging dogs showed a negative relationship with the residence time and the number of independent events of native scavenging species. Furthermore, their presence modified the hour of the peak in the activity patterns of the scavenger community. Implications for Conservation: The presence of free-ranging dogs may have important implications for the conservation of the Vulnerable Andean Condor ( Vultur gryphus) in Ecuador. To achieve the conservation goals of native vertebrate scavengers, particularly of Andean Condors, it is necessary to develop environmental education programs, provide technical training in responsible dog ownership, and conduct campaigns to sterilize and control dogs.

Aim: A current biogeographic paradigm states that climate regulates species distributions at continental scales and that biotic interactions are undetectable at coarse‐grain extents. However, advances in spatial modelling show that incorporating food resource distributions are important for improving model predictions at large distribution scales. This is particularly relevant to understand the factors limiting the distribution of widespread apex predators whose diets are likely to vary across their range.Location: Neotropical Central and South America.Methods: The harpy eagle (Harpia harpyja) is a large raptor, whose diet is largely comprised of arboreal mammals, all with broad distributions across Neotropical lowland forest. Here, we used a hierarchical modelling approach to determine the relative importance of abiotic factors and prey resource distribution on harpy eagle range limits. Our hierarchical approach consisted of the following modelling sequence of explanatory variables: (a) abiotic covariates, (b) prey resource distributions predicted by an equivalent modelling for each prey, (c) the combination of (a) and (b), and (d) as in (c) but with prey resources considered as a single prediction equivalent to prey species richness.Results: Incorporating prey distributions improved model predictions but using solely biotic covariates still resulted in a high‐performing model. In the Abiotic model, Climatic Moisture Index (CMI) was the most important predictor, contributing 76% to model prediction. Three‐toed sloth (Bradypus spp.) was the most important prey resource, contributing 64% in a combined Abiotic‐Biotic model, followed by CMI contributing 30%. Harpy eagle distribution had high environmental overlap across all individual prey distributions, with highest coincidence through Central America, eastern Colombia, and across the Guiana Shield into northern Amazonia.Main Conclusions: With strong reliance on prey distributions across its range, harpy eagle conservation programmes must therefore consider its most important food resources as a key element in the protection of this threatened raptor.