Costs of chick provisioning in cooperatively breeding crows: an experimental study

The costs of providing care to offspring and how these costs influence individual allocation of resources to current and future reproduction are likely to be important in the evolution of cooperative breeding. We reduced the costs of offspring care experimentally in 12 groups of cooperatively breeding carrion crows, Corvus corone corone, by providing supplementary food throughout the breeding season. Neither nonbreeders nor breeders from supplemented territories significantly increased their levels of provisioning effort. However, unfed crows lost more weight than fed crows and, in contrast to fed crows, lost weight in relation to provisioning effort. Furthermore, breeders decreased their provisioning rates in groups with more than three caregivers, supporting both the idea that provisioning chicks is costly and the conclusion that crows invest in self-maintenance rather than in the current brood when costs are reduced.