Costs of reproduction in a long-lived bird: Large clutch size is associated with low survival in the presence of a highly virulent disease

Department of Biology, Carleton University, Ottawa, Ontario, Canada K1A0H3.
Biology letters (Impact Factor: 3.25). 05/2009; 5(2):278-81. DOI: 10.1098/rsbl.2008.0704
Source: PubMed


Fitness costs of reproduction are expected to be more pronounced when the environmental conditions deteriorate. We took advantage of a natural experiment to investigate the costs of reproduction among common eiders (Somateria mollissima) nesting at a site in the Arctic, where an avian cholera epizootic appeared at different magnitudes. We tested the predictions that larger reproductive effort (clutch size) is associated with lower survival or breeding probability the following year, and that this relationship was more pronounced under heightened exposure to the disease. Our results indicate that large clutch sizes were associated with lower survival of female eider ducks, but only when there was heightened exposure to avian cholera, as indexed by eider mortality on site. No cost was observed when cholera was absent or when lesser exposure was evident. This supports the hypothesis that fitness costs of high reproductive effort are higher under unfavourable conditions such as a disease epizootic, and further indicates that being a conservative breeder can increase survival probability, given the presence of a highly virulent disease.

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    • "Similar results were found in at least two bird species using brood or clutch size manipulation ; individuals with increased parental care exhibited lower levels of antibodies or complement (Deerenberg et al. 1997; Berzins et al. 2011). Because immune traits considered here do not seem to mediate any prominent mechanisms affecting survival, we conclude that eiders may be more affected by avian cholera because of egg production and/or incubating larger clutches (Descamps et al. 2009) than by a slight reduction of their specific immunocompetence at the onset of reproduction . This reflects possible downregulation of the immune system to support higher costs of reproduction (Norris and Evans 2000). "
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