Social and genetic dynamics of extra -pair mating in waved albatrosses (Phoebastria irrorata)

Waved albatrosses (Phoebastria irrorata) are long-lived, socially monogamous seabirds with an unexpected incidence of extra-pair copulations (EPCs), and extra-pair fertilizations (EPFs) given the species' life history. In this study, behavioral and genetic data were used to examine predictions of hypotheses explaining variation in EPC behavior and its genetic consequences from the perspectives of both sexes. From the male perspective, early arrival timing to the breeding colony might confer benefits in terms of reproductive success if early arrival increases a male's extra-pair mating opportunities. While the earliest arriving males did engage in the most EPCs, earlier arrival did not translate into a higher probability of EPFs, such that the fitness advantages of early arrival remain unclear.;Several hypotheses relate variation in multiple mating among female birds to genetic, material, or social benefits. Data from three breeding seasons show mixed support for predictions of the good genes hypothesis whereby females engaging in EPCs gain fitness benefits of having chicks sired by males of better quality than their social mates. Female EPCs are not correlated with proximate measures of male quality although some support for the good genes idea extends to comparisons of behavior between cuckolded males and those that were never cuckolded. However, no differences in male body size, bill shape or EPC rate between pairs of cuckolded males and the genetic sires of the chicks they raise were demonstrated.;Strong philopatry inherent to this species' single-island endemism could set in motion mate choice that promotes inbreeding avoidance by females or EPF tolerance by cuckolded males when genetic sires are closely related; data from this study did not support either of these genetic hypotheses suggesting, instead, that benefits to females may be social or material and that males may adjust care in response to uncertain paternity. Support for social benefits of EPCs to females is not strong in the study population. Finally, waved albatross males appear to respond variably to uncertain paternity: within-pair copulations increase with female EPCs but measures of provisioning effort did not differ for cuckolded males. Taken together, these data suggest that promiscuity in waved albatrosses is a composite of social and genetic dynamics affected by both male and female behavior.