Publication Type: | Journal Article |
Year of Publication: | 1996 |
Authors: | CLOTFELTER, ETHAND |
Journal: | The Auk |
Volume: | 113 |
Issue: | 2 |
Date Published: | 1996 |
ISBN Number: | 00048038 |
Keywords: | bias, Estrildidae, Poephila, Poephila guttata, Taeniopygia, Taeniopygia guttata |
Abstract: | The offspring sex ratio at independence in a colony of Zebra Finches (Taeniopygia guttata) was significantly male biased. Three possible proximate causes of this bias were examined. (1) The first was that there is a sex-biased laying sequence followed by brood reduction. Males were significantly more likely to hatch from earlier-laid eggs than females, but there was no evidence of increased mortality among late-laid nestlings. (2) The second was that there is sex-biased mortality due to sex-specific growth rates. Male and female offspring had similar rates of mass increase, tarsus growth, and wing-chord growth. (3) The third was that there is sex-biased provisioning by one or both parents, increasing survival probabilities of preferred sex. There was evidence that males fed male-biased broods more frequently than female-biased broods. Fledging age, fledging mass, and the number of days to independence were similar for male and female offspring, suggesting that sex-biased provisioning had no significant biological effect. Although none of the hypotheses adequately explained the observed sex-ratio bias, results from this and other studies suggest that sex-biased laying sequences followed by brood reduction are most likely to cause skewed offspring sex ratios in nature. The implications of a sex-biased laying sequence and of sex-biased provisioning by the male are discussed in reference to the potential evolutionary conflict between males and females over control of offspring sex ratios. |
URL: | http://www.jstor.org/stable/4088910 |
Short Title: | The Auk |
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