Strong but variable associations between social dominance and clutch sex ratio in a colonial corvid

H. M. Salomons*, C. Dijkstra, S. Verhulst

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We studied primary sex ratio of clutches in relation to social dominance for 6 years in a colony of free-living jackdaws, a small corvid. Social dominance was strongly associated with clutch sex ratio, with the difference in clutch sex ratio between the most and least dominant pairs being 30-40%. To our knowledge, this is the first demonstration of an association between social dominance and sex allocation in birds. However, the direction of this effect varied between years. Dominant jackdaws produced more sons during the first years of the study but fewer sons during the last years. Offspring sex was not related to laying order within a clutch, and the effect of social dominance on sex ratio was similar on eggs laid first, middle, or last. We investigated the effect of 2 factors (laying date and parental condition) that could have mediated the shift in the effect of social dominance on sex allocation in the course of the study. Laying date was positively associated with the proportion of males, but this effect was independent of social dominance. Maternal condition (residual mass over tarsus and egg volume) was related to social dominance but not to clutch sex ratio. Paternal condition (residual mass over tarsus) was not related to clutch sex ratio. We discuss how spatial or temporal variation in effects of variables such as social dominance on sex allocation can contribute to our understanding of the evolution of sex allocation in species with complex life histories.

Original languageEnglish
Pages (from-to)417-424
Number of pages8
JournalBehavioral Ecology
Volume19
Issue number2
DOIs
Publication statusPublished - 2008

Keywords

  • body condition
  • corvidae
  • egg volume
  • resource holding potential
  • sex allocation
  • OFFSPRING SEX
  • PARUS-MAJOR
  • GREAT TIT
  • EGG SIZE
  • REPRODUCTIVE SUCCESS
  • MATERNAL CONDITION
  • PASSER-DOMESTICUS
  • HATCHING ORDER
  • HOUSE SPARROWS
  • BODY CONDITION

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