Density and extra-pair fertilizations in birds: A comparative analysis

David F. Westneat, Paul W. Sherman

Research output: Contribution to journalReview articlepeer-review

331 Scopus citations


Moller and Birkhead (1992, 1993) reported that extra-pair copulations (EPCs) occur more frequently in colonial than dispersed nesting birds. We comprehensively reviewed published data to investigate how breeding density affects extra-pair fertilizations (EPFs). Within species EPFs appeared to increase with density: two of three studies on colonial breeders and six of eight on dispersed nesters showed increases in EPFs with increasing density. However, comparisons among species (n = 72) revealed no evidence that EPF frequencies correlated with (1) nesting dispersion, (2) local breeding density, or (3) breeding synchrony, even when each of these variables in turn was held constant and phylogenetic relationships were taken into account via contrast analyses. Methodological and biological reasons for the disparity between observational studies of EPCs and molecular genetic analyses of EPFs are discussed.

Original languageEnglish
Pages (from-to)205-215
Number of pages11
JournalBehavioral Ecology and Sociobiology
Issue number4
StatePublished - Oct 1997


  • Breeding density
  • Contrast analyses
  • Dispersion
  • Extra-pair fertilizations
  • Synchrony

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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