Breeding synchrony and extra-pair mating in red-winged blackbirds

Patrick J. Weatherhead

Research output: Contribution to journalArticlepeer-review


Using data from a 6-year paternity study of red-winged blackbirds. I tested the hypotheses that increased nesting synchrony should either promote extra-pair mating by increasing the advantage of extra-pair mating to females, or decrease extra-pair mating by constraining males from seeking extra-pair copulations. Contrary to these hypotheses the occurrence of extra-pair paternity did not vary with nesting synchrony over the breeding season, or vary with the number of synchronous nests within territories or within marshes, or with nesting order on territories. However, for nearly all nests with extra-pair young, there were fewer females synchronous with that nest on the cuckolder's territory than on the territory of the cuckolded male. This 'advantage' of a synchrony difference was less pronounced for older males that cuckolded younger males, particularly when the two males were not neighbors. Collectively, these results suggest that breeding synchrony affects extra-pair mating by affecting mate guarding, but thai breeding synchrony alone can not be used to predict which females are more likely to engage in extra-pair mating, nor with which extra-pair males they will mate. Understanding why extra-pair mating by older males is less affected by breeding synchrony may explain much about both the proximate and ultimate causes of extra-pair mating in red-winged blackbirds.

Original languageEnglish (US)
Pages (from-to)151-158
Number of pages8
JournalBehavioral Ecology and Sociobiology
Issue number3
StatePublished - Mar 1997
Externally publishedYes


  • Age
  • Extra-pair mating
  • Neighbors
  • Red-winged blackbird
  • Synchrony

ASJC Scopus subject areas

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


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