Age, season and sex influence juvenile dispersal in the Iberian cinereous vultures (Aegypius monachus)

Abstract

Many aspects of the spatial ecology of the cinereous vulture (Aegypius monachus) are still unknown. The Iberian population is thought to be predominantly sedentary, but the spatial patterns of young individuals have been barely studied. The aim of this study was to provide a comprehensive understanding of the juvenile dispersal of the Iberian cinereous vultures. To this end, we GPS-tagged 41 Cinereous Vultures and tracked their movements during the period 2002–2021, from the end of parental care to the beginning of reproductive age. We examined the influence of age, season and sex on movement metrics (accumulated distances, distances to nest and home range sizes). During the juvenile dispersal period, cinereous vultures travelled over large areas of the Iberian Peninsula and southern Europe. Despite the high individual variability, we found a negative age-related trend in all movement metrics: the younger individuals (<1 year old) often performed farther movements and occupied larger areas, stabilising their movements during immature (1–3 years) and subadult (4 years) phases. On the other hand, season influenced the accumulated distance within all age classes; warm months positively influenced flight effort. Finally, females flew farther and occupied larger areas than males, consistently within age classes. This study did not take into account many factors which may explain part of the high variability observed: landscape, supplementary feeding sites, dumps, colony size, interspecific interactions, stochastic events, etc. Further studies are needed to investigate the influence of these factors on the dispersal of the species in more detail, but this work provides the first approach to the juvenile dispersal of the cinereous vulture in Iberia.