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Brood sex ratios, female harem status and resources for nestling provisioning in the great reed warbler (Acrocephalus arundinaceus)

Author:
  • Helena Westerdahl
  • Staffan Bensch
  • Bengt Hansson
  • Dennis Hasselquist
  • Torbjörn von Schantz
Publishing year: 2000
Language: English
Pages: 312-318
Publication/Series: Behavioral Ecology and Sociobiology
Volume: 47
Issue: 5
Document type: Journal article
Publisher: Springer

Abstract english

The theory of parental investment and brood sex ratio manipulation predicts that parents should invest in the more costly sex during conditions when resources are abundant. In the polygynous great reed warbler, Acrocephalus arundinaceus. females of primary harem status have more resources for nestling provisioning than secondary females, because polygynous males predominantly assist the primary female whereas the secondary female has to feed her young alone. Sons weigh significantly more than daughters, and are hence likely to be the more costly sex. In the present study, we measured the brood sex ratio when the chicks were 9 days old, i.e. the fledging sex ratio. As expected from theory, we found that female great reed warblers of primary status had a higher proportion of sons in their broods than females of lower (secondary) harem status. This pattern is in accordance with the results from two other species of marsh-nesting polygynous birds, the oriental reed warbler, Acrocephalus orientalis, and the yellow-headed blackbird Xanthocephalus xanthocephalus. As in the oriental reed warbler, we found that great reed warbler males increased their share of parental care as the proportion of sons in the brood increased. We did not find any difference in fitness of sons and daughters raised in primary and secondary nests. The occurrence of adaptive sex ratio manipulations in birds has been questioned, and it is therefore important that three studies of polygynous bird species, including our own, have demonstrated the same pattern of a male-biased offspring sex ratio in primary compared with secondary nests.

Keywords

  • Biological Sciences

Other

Published
  • Breeding ecology of great reed warblers
  • Wild great reed warblers
  • Molecular Ecology and Evolution Lab
  • ISSN: 1432-0762
Helena Westerdahl
E-mail: helena [dot] westerdahl [at] biol [dot] lu [dot] se

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MEMEG

+46 46 222 36 69

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Research group

Molecular Ecology and Evolution Lab

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Doctoral students and postdocs

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Luz Garcia-Longoria

PhD students, main supervisor

Samantha Mellinger

PhD students, assistant supervisor

Gustaf Ekelund Ugge

Helena Westerdahl w house sparrow