Female helpers signal their contribution to chick provisioning in a cooperatively breeding bird

Abstract

Behaviours whose primary function is not signalling can convey information that other individuals can use to make relevant decisions. In cooperatively breeding vertebrates, feeding young that are not own offspring typically provides indirect fitness payoffs, but group members may also benefit directly by advertising their contribution to their social mates, to either increase their ‘social prestige’ or obtain a share of territory commodities (‘pay to stay’). Evidence of such a signalling component of brood provisioning, however, remains controversial. In the cooperative society of carrion crows, Corvus corone , male subordinates have little chance of independent reproduction and do the best of a bad job by helping to raise the current brood. The value of future reproduction is instead higher for subordinate females, which, because they have better prospects of finding a breeding vacancy, generally invest less than males in helping at the nest. Under these circumstances, dominants are expected to be more vigilant over the contribution to brood provisioning by female subordinates, which in turn, might need to show their helpfulness to retain group membership. In accordance with this idea, we found that female retained offspring increased the ‘visibility’ of their contribution by provisioning in front of the dominant breeders significantly more than any other category of group members. In addition, retention of group membership for female offspring was associated with their perceived effort in chick feeding. Our results are consistent with the hypothesis of ‘pay to stay’ and suggest that a signalling component of helping can arise in a ‘typical’ kin-based cooperative society. • In carrion crows, retained offspring and immigrants help at the nests. • Female helpers often provision the brood in front of the dominant breeders. • Their perceived effort correlates with the probability of remaining in the group. • By advertising their work, they show that they are paying a rent for staying. • For female helpers, brood provisioning may therefore have a signalling component.