Is extrapair mating random? On the probability distribution of extrapair young in avian broods

Jon E. Brommer*, Peter Korsten, Karen M. Bouwman, Mathew L. Berg, Jan Komdeur

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Citations (SciVal)
33 Downloads (Pure)

Abstract

A dichotomy in female extrapair copulation (EPC) behavior, with some females seeking EPC and others not, is inferred if the observed distribution of extrapair young (EPY) over broods differs from a random process on the level of individual offspring (binomial, hypergeometrical, or Poisson). A review of the literature shows such null models are virtually always rejected, with often large effect sizes. We formulate an alternative null model, which assumes that 1) the number of EPC has a random (Poisson) distribution across females (broods) and that 2) the probability for an offspring to be of extrapair origin is zero without any EPC and increases with the number of EPC. Our brood-level model can accommodate the bimodality of both zero and medium rates of EPY typically found in empirical data, and fitting our model to EPY production of 7 passerine bird species shows evidence of a nonrandom distribution of EPY in only 2 species. We therefore argue that 1) dichotomy in extrapair mate choice cannot be inferred only from a significant deviation in the observed distribution of EPY from a random process on the level of offspring and that 2) additional empirical work on testing the contrasting critical predictions from the classic and our alternative null models is required.

Original languageEnglish
Pages (from-to)895-904
Number of pages10
JournalBehavioral Ecology
Volume18
Issue number5
Early online date13 Jul 2007
DOIs
Publication statusPublished - 01 Sept 2007
Externally publishedYes

Keywords

  • Extrapair copulation (EPC)
  • Likelihood
  • Mate choice
  • Null model
  • Sexual selection

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