Estimating expenditure on male and female offspring in a sexually size-dimorphic bird: A comparison of different methods

Michael J. L. Magrath*, Emile Van Lieshout, Ido Pen, G. Henk Visser, Jan Komdeur

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

29 Citaten (Scopus)
280 Downloads (Pure)


1. The parents of sexually size-dimorphic offspring are often assumed to invest more resources producing individuals of the larger sex. A range of different methods have been employed to estimate relative expenditure on the sexes, including quantifying sex-specific offspring growth, food intake, energy expenditure and energy intake, in addition to measures of parental food provisioning and energy expenditure. These methods all have the potential to provide useful estimates of relative investment, but each has particular problems of interpretation, and few studies have compared the estimates derived concurrently from more than two of these measures.

2. In this study we compared these surrogate measures of parental investment in the brown songlark Cinclorhamphus cruralis, which exhibits one of the most extreme cases of sexual size dimorphism among birds.

3. At 10 days of age we found that male chicks, on average, were 49% heavier, received 42% more prey items, expended 44% more energy and ingested 50% more metabolizable energy than their sisters.

4. Furthermore, we created, experimentally, both all-male and all-female broods of 10-day-old chicks and found that mothers delivered 43% more prey items and expended 27% more energy when provisioning all-male broods, providing the first direct evidence for a change in parental energy expenditure in relation to brood sex ratio.

5. These data reveal remarkable agreement between these estimates of investment and suggest that all may provide quantitatively useful information on sex allocation. However, the lower variance associated with estimates of relative mass and energy intake suggest that these methods may be of greater utility, although this may primarily reflect the shorter period over which our provisioning data were collected.

Originele taal-2English
Pagina's (van-tot)1169-1180
Aantal pagina's12
TijdschriftJournal of Animal Ecology
Nummer van het tijdschrift6
StatusPublished - nov.-2007

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