Winter movement patterns of a globally endangered avian scavenger in south-western Europe

Abstract

Partial migration, whereby some individuals migrate and some do not, is relatively common and widespread among animals. Switching between migration tactics (from migratory to resident or vice versa) occurs at individual and population levels. Here, we describe for the first time the movement ecology of the largest wintering population of Egyptian Vultures (Neophron percnopterus) in south-west Europe. We combined field surveys and GPS tracking data from December to February during four wintering seasons (2014–2018). The wintering population consisted on average of 85 individuals (range 58–121; 76% adults and 24% subadults). Individuals were counted at five different roosting sites located near farms, unauthorized carcass deposition sites and authorized carcass deposition sites. Our results show that vultures tend to remain close to the roosting site. Moreover, we observed that females exhibited smaller home range sizes than males, which suggests a possible differential use of food sources. Overall, birds relied more on farms than other available food resources, particularly subadult individuals which exploited more intensively these sites. Our results showed that Egyptian Vultures congregate in significant numbers at specific sites throughout the winter period in south-west Spain and that these roosting and feeding sites should be given some level of legal protection and regular monitoring. Furthermore, predictable food sources might be driving the apparent increase in the non-migratory population of Egyptian Vultures, as observed in other avian species which are also changing their migratory behavior.

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

“…We therefore caution that our conclusions of the relative survival benefit of migration rest on the assumption that monthly survival probability at northern latitudes outside of the breeding season is not higher than during the breeding season. We encourage tests of this hypothesis with data that may become available in the near future (Morant et al., 2020).…”

Environmental and social correlates, and energetic consequences of fitness maximisation on different migratory behaviours in a long-lived scavenger

“…Appendix S1 for details). We accessed to two sources of data: 1) data from the Spanish Ornithological Society, in which the wintering population was monitored on a yearly basis by censusing individuals (without differentiation of age classes) in January between 2006 and 2019; 2) our own monitoring project, where the wintering population was monitored twice monthly from December to February between 2014 and 2019 with adults and subadults classi ed according to plumage characteristics (more details in Morant et al 2020). In the rst case, censuses were carried out in one roosting site until 2014.…”

“…This endangered species ranges across southern Europe, northern Africa, the Middle East and Central and South Asia (BirdLife International 2020). While migratory individuals regularly travel >4,000 km between their northern breeding and southern wintering grounds by using several distinct migratory yways (Phipps et al 2019;Buechley et al 2021), other individuals overwinter in southern and south-western Spain (García et al 2000;Morant et al 2020). The Egyptian Vulture is an obligate scavenger that frequently consumes both carrion from livestock and wild ungulates (Donázar 1993).…”

Management Actions Promote Human-Wildlife Coexistence in Highly Anthropized Landscapes: The Case of an Endangered Avian Scavenger

“…The Egyptian Vulture (Neophron percnopterus) is a mediumsized, long-lived, monogamous, scavenger (Ferguson-Lees and Christie, 2001). Western European mainland populations spend the winter (and usually their first year of life) in the sub-Saharan Sahel region (Phipps et al, 2019), although a non-migrant population was detected in South-western Spain (Morant et al, 2020a). It is listed as globally endangered due to severe declines experienced throughout its range (BirdLife International, 2020).…”