Mothers adjust offspring sex to match the quality of the rearing environment

Sarah R. Pryke, Lee A. Rollins

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


Theory predicts that mothers should adjust offspring sex ratios when the expected fitness gains or rearing costs differ between sons and daughters. Recent empirical work has linked biased offspring sex ratios to environmental quality via changes in relative maternal condition. It is unclear, however, whether females can manipulate offspring sex ratios in response to environmental quality alone (i.e. independent of maternal condition). We used a balanced within-female experimental design (i.e. females bred on both low- and high-quality diets) to show that female parrot finches (Erythrura trichroa) manipulate primary offspring sex ratios to the quality of the rearing environment, and not to their own body condition and health. Individual females produced an unbiased sex ratio on high-quality diets, but over-produced sons in poor dietary conditions, even though they maintained similar condition between diet treatments. Despite the lack of sexual size dimorphism, such sex ratio adjustment is in line with predictions from sex allocation theory because nutritionally stressed foster sons were healthier, grew faster and were more likely to survive than daughters. These findings suggest that mothers may adaptively adjust offspring sex ratios to optimally match their offspring to the expected quality of the rearing environment.

Original languageEnglish
Pages (from-to)4051-4057
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1744
Publication statusPublished - 7 Oct 2012


  • Maternal condition
  • Maternal diet
  • Nutrition quality
  • Sex allocation
  • Sex-specific costs

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