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

David F. Westneat, Ian R.K. Stewart

Research output: Contribution to journalReview articlepeer-review

553 Scopus citations


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.

Original languageEnglish
Pages (from-to)365-396
Number of pages32
JournalAnnual Review of Ecology, Evolution, and Systematics
StatePublished - 2003


  • Comparative approach
  • Extra-pair copulation
  • Game theory
  • Reproductive strategy
  • Selection theory
  • Sexual selection

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology


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