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

P Bize*, A Roulin, JL Tella, H Richner

*Corresponding author for this work

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

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 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.

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 phytohaemagglutinin (PHA) in another year.

4. There 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.

5. Our 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.

Original languageEnglish
Pages (from-to)405-413
Number of pages9
JournalFunctional Ecology
Volume19
Issue number3
DOIs
Publication statusPublished - Jun 2005

Keywords

  • Hippoboscidae
  • immunocompetence
  • phytohaematogglutinin
  • sex-specific mortality
  • sibling competition
  • SEXUAL SIZE DIMORPHISM
  • CELL-MEDIATED-IMMUNITY
  • IMMUNOCOMPETENCE HANDICAP
  • FIELD EXPERIMENTS
  • RATIO ADJUSTMENT
  • PIED FLYCATCHERS
  • LIFE-HISTORY
  • BIRDS
  • SELECTION
  • CHICK

Cite this

Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings. / Bize, P; Roulin, A; Tella, JL; Richner, H.

In: Functional Ecology, Vol. 19, No. 3, 06.2005, p. 405-413.

Research output: Contribution to journalArticle

Bize, P ; Roulin, A ; Tella, JL ; Richner, H. / Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings. In: Functional Ecology. 2005 ; Vol. 19, No. 3. pp. 405-413.
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AB - 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 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.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 phytohaemagglutinin (PHA) in another year.4. There 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.5. Our 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.

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