Drivers of alloparental provisioning of fledglings in a colonially-breeding bird

Offspring provisioning represents a major reproductive cost. However, evidence suggests that parents sometimes feed unrelated offspring. Several hypotheses could explain this puzzling phenomenon. Adults could feed unrelated offspring that are (1) of close social associates to facilitate these juveniles’ integration into their social network (resulting in social inheritance), (2) potential extra-pair offspring, (3) at a similar developmental stage as their own, (4) coercing feeding by begging, or (5) less-developed and who’s enhanced survival would benefit the adult or its own offspring (the group augmentation hypothesis). Colonial breeders are ideal for investigating the relative importance of these hypotheses because offspring are often kept in crèches where adults can exhibit allofeeding. Using automated monitoring of replicated captive zebra finch (Taeniopygia guttata) colonies, we found that while parents selectively fed their own offspring, they also consistently fed unrelated offs...