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Paternal care in the cooperatively polyandrous Galapagos Hawk

Abstract:

In cooperative breeding systems, males that share a nest face the prospect of providing for young that are not their own. Males of many species attempt to reduce the risk of losing paternity with aggressive behaviors, thereby limiting other males' access to the female during copulation. The Galapagos Hawk (Buteo galapagoensis) exhibits an extreme form 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 territory are unrelated adults and share paternity. We examine paternal care in relation to the shared parentage of the Galapagos Hawk and offer explanations for group cohesion. We found that paternal care was variable and that all males cared for the young on their territory without regard to the number of males residing together. There was evidence 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 between paternity and care. There was no obvious cue the males could use to discern paternity, since the only evidence of dominance was a subtle hierarchy expressed in larger groups. We suggest that the simple rule for paternal care in the Galapagos Hawk is that if a male is a group member, he will copulate with the female, have some probability to fertilize the eggs, and provide care for young produced at the nest.