The influence of siblings on begging behaviour

Elaborate solicitation displays are a common feature of interactions between care-givers and offspring. These displays are interpreted as the phenotypic expression of the conflict of interests between parents and offspring over parental investment. Offspring typically have siblings and thus do not exist in isolation. Therefore, they may adjust their begging in response to their siblings' begging, either competitively or cooperatively. Alternatively, begging may be independent of the begging efforts of siblings. Studies of avian begging have primarily focused on nestlings, where offspring are immobile and compete directly over the allocation of parental resources. We investigated the influence sibling begging had on individual fledgling begging in the cooperatively breeding pied babbler, Turdoides bicolor. Using experimental manipulations, we found that fledgling begging behaviour was negatively correlated with satiation and unrelated to the begging effort of siblings. Pied babbler care-givers were able to target increased provisioning to individuals with artificially increased demand while maintaining provisioning rates to the rest of the brood. Thus, fledglings were found to incur no provisioning costs or benefits from either increased or decreased begging by their siblings. We propose that the combination of targeted provisioning, flexible levels of provisioning and the dispersed nature of fledglings reduces the benefits of competitive or cooperative begging in this species.