Alloparental care in the common murre (Uria aalge)

Abstract

Common murres (Uria aalge) at the Gannet Islands, Labrador, were found to assist in the rearing of chicks which were not their own. This alloparental behaviour was most common among birds which had failed in their breeding attempt and mainly comprised brooding of well-grown chicks aged 18–22 days. Alloparental care occurred both when the chick's parents were present and absent from the colony. It is unusual for common murre chicks to be left unattended and occurs only when food availability is low: alloparents may increase the chances of survival of unattended chicks. There are several possible explanations for alloparental care in common murres, but at the present time we have insufficient information to enable us to distinguish between them. However, the most parsimonious explanation is that chicks take advantage of a nonadaptive residual hormone titre in failed breeders.