Extra-Pair Paternity in Birds: Causes, Correlates, and Conflict

TLDR

Extra‑pair paternity in birds varies widely in frequency and the behaviors that produce it, and while many studies have suggested a female‑strategy bias, conflict theory predicts that adaptations of all participants generate complex, highly variable mating patterns. The study evaluates the behavioral events that lead to extra‑pair paternity and argues that the evidence supporting a female‑strategy bias is weak. The authors propose that testing conflict‑theory predictions requires detailed data on male‑female encounters, post‑encounter behavior, and fertilization dynamics. The results support some conflict‑theory predictions yet leave room for alternative explanations, and the evidence for a female‑strategy bias is weak.

Abstract

▪ Abstract Extra-pair paternity (EPP) is extremely variable among species of birds, both in its frequency and in the behavioral events that produce it. A flood of field studies and comparative analyses has stimulated an array of novel ideas, but the results are limited in several ways. The prevailing view is that EPP is largely the product of a female strategy. We evaluate what is known about the behavioral events leading to EPP and find the justification for this view to be weak. Conflict theory (derived from selection theory) predicts that adaptations in all the players involved will influence the outcome of mating interactions, producing complex and often highly variable patterns of behavior and levels of EPP. Data support some of these predictions, but alternative hypotheses abound. Tests of predictions from conflict theory will require better information on how males and females encounter one another, behave once they have met, and influence fertilization once insemination has occurred.