Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings

1) Sex-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. 2) Here, we investigated sex-specific susceptibility to the blood-sucking louse fly Crat rina melb 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. 3) For this purpose, we manipulated ectoparasite loads by adding or removing flies to randomly chosen nests in two years, and injected nestlings with mitogenic phytoh magglutinin (PHA) in another year.

P. Bize, A. Roulin, J. L. Tellas and H. Richner, Functional Ecology 2005 19, 405-413