PATERNAL CARE IN THE COOPERATIVELY POLYANDROUS GALAPAGOS HAWK

In cooperative breeding systems, males that share a nest face the pros pect of providing for young that are not their own. Males of many spec ies attempt to reduce the risk of losing paternity with aggressive beh aviors, thereby limiting other males' access to the female during copu lation. The Galapagos Hawk (Buteo galapagoensis) exhibits an extreme f orm of cooperative polyandry in which anecdotal data suggest all males in a territory share mating equally with the female, with very little to no interference, and care for young within the group. Males in a t erritory are unrelated adults and share paternity. We examine paternal care in relation to the shared parentage of the Galapagos Hawk and of fer explanations for group cohesion. We found that paternal care was v ariable and that all males cared for the young on their territory with out regard to the number of males residing together. There was evidenc e that males that sired young and those that sired none did not differ in quantity of care. However, we could not rule out a relationship be tween paternity and care. There was no obvious cue the males could use to discern paternity, since the only evidence of dominance was a subt le hierarchy expressed in larger groups. We suggest that the simple ru le for paternal care in the Galapagos Hawk is that ifa male is a group member, he will copulate with the female, have some probability to fe rtilize the eggs, and provide care for young produced at the nest.