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- Title
Offspring sex ratio varies with clutch size for female house wrens induced to lay supernumerary eggs.
- Authors
Bowers, E. Keith; Thompson, Charles F.; Sakaluk, Scott K.
- Abstract
Mothers adjust the sex of their offspring strategically to maximize fitness. Theory predicts that high-quality mothers should over-produce sons, but whether or not this occurs in nature is subject to debate. Here, we show that female house wrens capable of laying more eggs than normal produced a higher proportion of sons than females laying fewer eggs. Last-laid eggs were also more likely to contain daughters than earlier-laid eggs.Theory predicts that a mother’s ability to produce high-quality offspring should influence whether she produces sons or daughters. We tested this hypothesis in house wrens (Troglodytes aedon) using a within-clutch design in which we induced females to produce more eggs (8–10 eggs) than they normally would (6 or 7 eggs) to determine whether maternal effort and the allocation of resources to supernumerary eggs (those laid beyond the usual number) influence the offspring sex ratio. At the clutch level, we predicted that high-quality females, as defined by their ability to produce supernumerary eggs in response to egg removal, would overproduce sons relative to females treated the same way but producing fewer eggs. At the level of the egg, we predicted that supernumerary eggs would more likely contain daughters than sons. As predicted, females producing extralarge clutches overproduced sons and those producing smaller clutches produced relatively more daughters. Last-laid eggs were also more likely to contain daughters than earlier-laid eggs although there was no difference in the mass of eggs containing males and females. These results suggest that mothers adjust the sex of their offspring strategically to maximize fitness.
- Subjects
WRENS; SONGBIRDS; ANIMAL clutches; BIRD reproduction; PARENTAL behavior in animals; ANIMAL behavior; BIRDS
- Publication
Behavioral Ecology, 2014, Vol 25, Issue 1, p165
- ISSN
1045-2249
- Publication type
Article
- DOI
10.1093/beheco/art100