Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings
Article first published online: 24 JUN 2005
Volume 19, Issue 3, pages 405–413, June 2005
How to Cite
BIZE, P., ROULIN, A., TELLA, J. L. and RICHNER, H. (2005), Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings. Functional Ecology, 19: 405–413. doi: 10.1111/j.1365-2435.2005.00995.x
- Issue published online: 24 JUN 2005
- Article first published online: 24 JUN 2005
- Received 6 December 2004; revised 3 March 2005; accepted 10 March 2005
- sex-specific mortality;
- sibling competition
- 1Sex-biased mortality in adult vertebrates is often attributed to lower immunocompetence and higher parasite susceptibility of males. Although sex-specific mortality has also been reported during growth, the importance of sex-specific immunocompetence and parasite susceptibility in explaining male-biased mortality remains ambiguous in growing individuals because of potentially confounding sources of mortality such as sexual dimorphism.
- 2Here, we investigated sex-specific susceptibility to the blood-sucking louse fly Crataerina melbae and sex differences in cell-mediated immunity in a bird species that is sexually monomorphic both in size and plumage coloration at the nestling stage, the Alpine Swift, Apus melba.
- 3For this purpose, we manipulated ectoparasite loads by adding or removing flies to randomly chosen nests in two years, and injected nestlings with mitogenic phytohaemagglutinin (PHA) in another year.
- 4There were no significant differences between male and female offspring in immune response towards PHA, parasite load, and parasite-induced decrease in growth rate. Secondary sex ratios were however biased toward males in parasitized broods, and this was explained by a greater mortality of females in parasitized than deparasitized broods.
- 5Our findings are in contrast to the widely accepted hypothesis that males suffer a greater cost of parasitism. We discuss alternative hypotheses accounting for female-specific mortality.