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Sex and environmental sensitivity in blue tit nestlings

Author:
  • Lars Råberg
  • Martin Stjernman
  • Jan-Åke Nilsson
Publishing year: 2005
Language: English
Pages: 496-503
Publication/Series: Oecologia
Volume: 145
Issue: 3
Document type: Journal article
Publisher: Springer

Abstract english

In birds and mammals with sexual size dimorphism (SSD), the larger sex is typically more sensitive to adverse environmental conditions, such as food shortage, during ontogeny. However, some recent studies of altricial birds have found that the larger sex is less sensitive, apparently because large size renders an advantage in sibling competition. Still, this effect is not an inevitable outcome of sibling competition, because several studies of other species of altricial birds have found the traditional pattern. We investigated if the sexes differ in environmental sensitivity during ontogeny in the blue tit, a small altricial bird with c. 6% SSD in body mass (males larger than females). We performed a cross-fostering and brood size manipulation experiment during 2 years to investigate if the sexes were differently affected as regards body size (body mass, tarsus and wing length on day 14 after hatching) and pre-fledging survival. We also investigated if the relationship between body size and post-fledging survival differed between the sexes. Pre-fledging mortality was higher in enlarged than in reduced broods, representing poor and good environments, respectively, but the brood size manipulation did not affect the mortality rate of males and females differently. In both years, both males and females were smaller on day 14 after hatching in enlarged as compared to reduced broods. In one of the years, we also found significant Sex x Experiment interactions for body size, such that females were more affected by poor environmental conditions than that of males. Body size was positively correlated with post-fledging survival, but we found no interactive effects of sex and morphological traits on survival. We conclude that in the blue tit, females (the smaller sex) are more sensitive to adverse environmental conditions which, in our study, was manifest in terms of fledgling size. A review of published studies of sex differences in environmental sensitivity in sexually size-dimorphic altricial birds suggests that the smaller sex is more sensitive than the larger sex in species with large brood size and vice versa.

Keywords

  • Biological Sciences

Other

Published
  • Molecular Ecology and Evolution Lab
  • ISSN: 1432-1939
Martin Stjernman
E-mail: martin [dot] stjernman [at] biol [dot] lu [dot] se

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Biodiversity

+46 46 222 38 20

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Biodiversity and Conservation Science

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Predicting effects of the common agricultural policy on farmland birds

Doctoral students and postdocs

PhD students, assistant supervisor

Gabriel Norevik

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