Sex-Biased Hatching Order and Adaptive Population Divergence in a Passerine Bird

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Science  11 Jan 2002:
Vol. 295, Issue 5553, pp. 316-318
DOI: 10.1126/science.1066651

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Most species of birds can lay only one egg per day until a clutch is complete, and the order in which eggs are laid often has strong and sex-specific effects on offspring growth and survival. In two recently established populations of the house finch (Carpodacus mexicanus) in Montana and Alabama, breeding females simultaneously adjusted the sex and growth of offspring in relation to their position in the laying order, thereby reducing the mortality of sons and daughters by 10 to 20% in both environments. We show experimentally that the reduction in mortality is produced by persistent and sex-specific maternal effects on the growth and morphology of offspring. These strong parental effects may have facilitated the rapid adaptive divergence among populations of house finches.

  • * Present address: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.

  • To whom correspondence should be addressed. E-mail: abadyaev{at}

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