Pair duration, breeding success and divorce in a long-lived seabird: benefits of mate familiarity?

Previous studies have reported that pair duration is positively related to breeding performance and negatively related to divorce probability. According to the concept of ‘mate familiarity’, a long-term improvement in pair coordination with pair duration results in increased breeding performance. We assessed whether breeding experience, costs of mate change, individual quality and prior residence explained relationships involving pair duration in the kittiwake, Rissa tridactyla. We used specific samples (groups of individuals) where confounding factors were not relevant. In the complete data set (a heterogeneous group of individuals), breeding success probability increased with pair duration. Such variation in fitness may reflect changes at the individual level, or in the proportion of individuals of different quality. Breeding experience accounted for a sharp increase in success probability between the first and second years of pair duration. This trend was not observed in new pairs composed of only experienced breeders. Success probability did not increase with pair duration within groups of pairs with the same total duration, or in high-quality birds (using longevity as an index of quality). Finally, mate fidelity and site fidelity may be confounding factors. Prior residence (length of residence at the nest site) better explained variation in success and divorce probabilities than did pair duration. Overall, we found no evidence of a continuous increase in success probability with pair history that could be attributed to mate familiarity. This study highlights the need to consider within-population heterogeneity when assessing the evolution of life history traits.