Abstract
Sex biases in the allocation of resources to offspring occur in a broad range of taxa. Parents have been shown to achieve such biases either by producing numerically more of one sex or by providing the individuals of one sex with a greater quantity of resources. In addition, skews in allocation could occur if the offspring of one sex receive resources of higher quality (greater nutritional or energetic value by weight or volume), although this mode of adjustment has, to our knowledge, never been demonstrated. We compared the types of prey and the metabolizable energy provisioned to male and female nestlings in one of the most sexually size dimorphic of all birds, the brown songlark, Cinclorhamphus cruralis. Within broods, we found that males not only received more prey than their smaller sisters, but also prey of apparently higher quality. This dietary disparity could result either from mothers actively discriminating between the sexes when providing prey or from competition among siblings. We suggest that sex differences in offspring diet quality may occur in a wide range of other taxa and function as an additional mechanism of sex allocation adjustment.
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Selected References
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- Hunter M. S., Woolley J. B. Evolution and behavioral ecology of heteronomous aphelinid parasitoids. Annu Rev Entomol. 2001;46:251–290. doi: 10.1146/annurev.ento.46.1.251. [DOI] [PubMed] [Google Scholar]
- Visser G. H., Schekkerman H. Validation of the doubly labeled water method in growing precocial birds: the importance of assumptions concerning evaporative water loss. Physiol Biochem Zool. 1999 Nov-Dec;72(6):740–749. doi: 10.1086/316713. [DOI] [PubMed] [Google Scholar]