Secondary sex ratio adjustment in red-winged Blackbirds (Agelaius phoeniceus)

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Abstract

Red-winged Blackbird (Agelaius phoeniceus) offspring sex ratios at hatch were determined for 97 clutches suffering no egg loss or infertility and produced an overall sex ratio of 1 male: 0.94 females. Offspring sex ratios varied seasonally, with early and late initiating females producing more female offspring and mid-season initiators producing more males. While this pattern is in keeping with the assumed pattern of seasonal resource abundance, the sex ratio biases seen were at best only slight. Using two measures of male quality, no support was found for the hypothesis that females should preferentially produce sons when mated to high quality males. The data did suggest, however, that females may reduce the variance in offspring sex ratios in larger harems. Some alternative interpretations are presented.

Original languageEnglish (US)
Pages (from-to)57-61
Number of pages5
JournalBehavioral Ecology and Sociobiology
Volume12
Issue number1
DOIs
StatePublished - Mar 1 1983
Externally publishedYes

ASJC Scopus subject areas

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

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