Abstract Group living can provide antipredator benefits through collective vigilance, but individual contributions to vigilance often vary with experience and age. In this study, we investigated whether adult carrion crows ( Corvus corone ) adjust their vigilance depending on group composition, particularly the presence of less vigilant yearlings. In a family living population of crows in Northern Spain, we compared the vigilance behavior of yearlings and adults and we analyzed whether adults’ vigilance varied depending on the composition of the group. Yearlings were significantly less vigilant than adults. Adult crows significantly reduced their vigilance rate as the number of adult group members increased, but effectively ignored yearlings when setting their vigilance effort. These findings support the idea that adults finely adjust their antipredator behavior based on the number of experienced group members rather than the total number of individuals. Nevertheless, yearlings may still benefit by foraging near tolerant adults within family groups, gaining protection without incurring competition costs. This dynamic may play a role in promoting yearling delayed dispersal, creating the conditions that favor cooperative breeding. Our study highlights the nuanced mechanisms by which social factors influence vigilance in group-living animals.
Gómez et al. (Fri,) studied this question.