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Interfemale variation in egg yolk androgen allocation in the European starling: do high-quality females invest more?

  • KM Pilz
  • Henrik Smith
  • Maria Sandell
  • H Schwabl
Publishing year: 2003
Language: English
Pages: 841-850
Publication/Series: Animal Behaviour
Volume: 65
Issue: 4
Document type: Journal article
Publisher: Elsevier

Abstract english

Androgenic hormones occur naturally in bird egg yolk and are known to enhance growth in canary and gull chicks. Gil et al. (1999, Science, 286, 126-128) have recently proposed that female allocation of androgens to eggs represents a form of costly maternal investment. This hypothesis predicts that females of high quality or high reproductive potential should invest more yolk androgens in their eggs than females of low quality or low reproductive potential. We tested these predictions by examining interfemale variation in allocation of the androgenic steroids testosterone and androstenedione to eggs in a wild population of European starlings, Sturnus vulgaris. We collected 30 full clutches of eggs and captured 22 of the females that laid these clutches for phenotypic measurements. In agreement with the hypothesis, we found that there was significant interfemale variation in yolk androgen concentrations. Furthermore, older females deposited more androstenedione and testosterone in eggs than 1-year-old females, and females laying early or large clutches deposited more testosterone in eggs than females laying late or small clutches. However, females in good body condition did not deposit more androgens in eggs than females in poor body condition. Large-yolked eggs had a higher total yolk androgen content than small-yolked eggs, but larger eggs did not have higher concentrations of yolk androgens. The results in general support the investment hypothesis of yolk androgen allocation. However, further data are needed regarding the costs of yolk androgen allocation and the effects of yolk androgens on offspring to substantiate the assumptions of the hypothesis.


  • Ecology


  • ISSN: 1095-8282
Henrik Smith
E-mail: henrik [dot] smith [at] biol [dot] lu [dot] se



+46 46 222 93 79

+46 70 978 20 56




Centre for Environmental and Climate Research (CEC)

+46 46 222 93 79

+46 70 978 20 56


Sölvegatan 37, Lund


Centre for Animal Movement Research
Evolutionary Ecology, Department of Biology
Ecology building S-223 62 Lund Sweden