Mercedes Burgueño, Paul James Haverkamp, Michael Griesser

Predation is a critical selective force, facilitating the evolution of anti-predatory behaviours, such as vigilance. However, this behaviour can also be used to monitor conspecifics. Here we evaluate the antipredator and social functions of vigilance in Siberian jays. In this bird species, groups can include retained offspring that remain with their parents well beyond independence, as well as non-kin non-breeders. Mixed models showed that breeders in groups with retained offspring increased vigilance in older, open forest patches more suitable for hawk hunting. Moreover, breeders increased their vigilance in groups with more non-kin members, particularly away from forest edges where tracking of group members is more difficult. Finally, female breeders maintained their vigilance in groups with more non-kin members while males reduced vigilance, reflecting a larger need for social monitoring as male non-kin are often dominant over female breeders. These findings highlight that both predation risk and social factors influence the investment in vigilance.