Intra-specific competition in foraging Griffon Vultures Gyps fulvus: 2. The influence of supplementary feeding management

Abstract

Capsule Young vultures have better access to food resources at supplementary feeding sites where carcasses are fewer and less predictable, and placed further from colonies.Aims To investigate the impact of the management of supplementary feeding sites on foraging and feeding behaviour in Griffon Vultures Gyps fulvus.Methods With focal and scan sampling we studied whether group size, group composition and foraging behaviour differed between collective ‘heavy’ feeding sites (sites close to colonies, supplied regularly with many carcasses) and individual ‘light’ feeding sites (sites further from colonies, supplied irregularly with few carcasses).Results Total group size was proportional to food mass deposited and did not differ between sites in summer. At heavy feeding sites adults arrived sooner than young, so they had better access to viscera of high energy content, while young individuals could only eat later on the scraps. However, at light feeding sites young vultures arrived earlier and in larger proportions. Intra-specific competition was strong and adults were generally dominant over younger birds.Conclusions Young birds foraged preferentially at light feeding sites where the competition was lower, allowing a better access to high-quality food. Favouring light feeding sites is an adequate solution for managing vulture populations in areas in which sanitary laws permit carcasses to be placed at feeding sites.