Drivers of alloparental provisioning of fledglings in a colonially-breeding bird (Q9123)

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 offspring (32.48% of feeding events). Social relationships among adults prior to breeding did not predict allofeeding, nor was provisioning directed towards unrelated offspring directed to potential genetic offspring. Instead, adults preferentially fed less-developed non-offspring, despite these not begging more frequently than larger ones did. Our study suggests that allofeeding is consistent with group augmentation, which could be beneficial through colony maintenance or increased offspring survival.