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Optimizing the trade-off between offspring number and quality in unpredictable environments: Testing the role of differential androgen transfer to collared flycatcher eggs

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Author

  • Amber M. Rice
  • Niclas Vallin
  • Katarzyna Kulma
  • Hanna Arntsen
  • Arild Husby
  • Michael Tobler
  • Anna Qvarnstrom

Summary, in English

According to the brood reduction hypothesis, parents adjust their brood size in response to current environmental conditions. When resources are abundant, parents can successfully raise all hatched offspring, but when resources are scarce, brood reduction, i.e., the sacrifice of some siblings to secure the quality of a subset of offspring, may maximize fitness. Differential transfer of maternal androgens is one potential proximate mechanism through which female birds may facilitate brood reduction because it may alter the relative competitive ability of sibling nestlings. We tested the hypothesis that female collared flycatchers (Ficedula albicollis) manipulate sibling competition by transferring less androgens to eggs late in the laying sequence. We experimentally elevated androgen levels in i) whole clutches and ii) only the two last laid eggs, and compared growth and begging behavior of offspring from these treatments with a control treatment. By using three treatments and video assessment of begging, we examined the effects of within-clutch patterns of yolk androgen transfer on levels of sibling competition in situ. When androgens were elevated in only the two last laid eggs, begging was more even among siblings compared to control nests. We also found that female nestlings receiving additional yolk androgens showed higher mass gain later in the breeding season, while their male counterparts did not. Our results suggest that females may improve reproductive success in unpredictable environments by altering within-clutch patterns of yolk androgen transfer. We discuss the possibility that life-history divergence between the co-occurring collared and pied flycatcher (Ficedula hypoleuca) is amplified by patterns of yolk androgen transfer. (C) 2013 Elsevier Inc. All rights reserved.

Publishing year

2013

Language

English

Pages

813-822

Publication/Series

Hormones and Behavior

Volume

63

Issue

5

Document type

Journal article

Publisher

Elsevier

Topic

  • Biological Sciences

Keywords

  • Androstenedione
  • Begging
  • Brood reduction hypothesis
  • Collared
  • flycatcher
  • Laying order
  • Maternal effects
  • Parent-offspring conflict
  • Sex-specific effects
  • Sibling competition
  • Testosterone

Status

Published

Project

  • Immunoecology

Research group

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Other

  • ISSN: 1095-6867