Who are we feeding? Asymmetric individual use of surplus food resources in an insular population of the endangered Egyptian vulture Neophron percnopterus.

Abstract

Supplementary feeding stations, or "vulture restaurants", are common conservation management tools. While a number of studies have investigated the consequences of surplus food on the population dynamics of scavengers, relatively little is known about the effects of such practices at the individual level. Within the long-term monitored breeding population of Canarian Egyptian vultures (Neophron percnopterus majorensis) we investigated individual bird's patterns of use of a supplementary feeding station at Fuerteventura (Canary Islands), over the course of breeding (2001, 2002; 2004-2011) and non-breeding seasons (2000-2010). Our results show that during the breeding season the individual use of the supplementary feeding station was inversely related to the distance to the breeding territory, which suggests the existence of central-place foraging constraints. In addition, larger birds of poor body-condition and individuals that ultimately failed to fledge young were detected more frequently at the feeding station. During the non-breeding season, and because most breeding birds abandoned the breeding territories, the overall abundance of Egyptian vultures at the feeding station grew. Moreover, the only variable increasing the probability of presence of individuals was poor body condition so that birds with lower wing residual visited the feeding station more frequently. Supplementary feeding may benefit individuals who would otherwise have been subject to selective pressures. From our results it follows that this conservation strategy must be used with caution because it can have consequences on an individual level and thus potentially affect the viability of endangered populations.