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Egg yolk androgen levels increase with breeding density in the European Starling, Sturnus vulgaris

  • K M Pilz
  • Henrik Smith
Publishing year: 2004
Language: English
Pages: 58-66
Publication/Series: Functional Ecology
Volume: 18
Issue: 1
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

1. High breeding density can cause elevated plasma androgen levels in adult birds. Since maternal androgens are deposited into egg yolk, high breeding density may result in elevated yolk androgen levels as well. 2. The relationship between breeding density and yolk androgen levels was examined in the European Starling, Sturnus vulgaris. The concentration and total content of yolk androstenedione and yolk testosterone were measured in eggs from 24 clutches distributed across nine different colonies of nestboxes. 3. Yolk androstenedione and testosterone levels were significantly higher in colonies where a greater proportion of nestboxes had active nests. 4. Yolk testosterone levels were significantly higher, and yolk androstenedione levels were marginally higher, in colonies with a greater absolute number of active nests. 5. Yolk androgen levels were not related to the number of active nests in adjacent nestboxes. 6. We conclude that female starlings nesting in colonies with higher breeding densities transfer more androgen to their eggs. 7. This relationship may be mediated by increased interfemale aggression, particularly towards floater females searching for mates or nests to brood parasitize, in high-density colonies. Such a relationship between maternal environment and maternal yolk androgens may represent adaptive maternal modification of offspring phenotype or a non-adaptive physiological constraint which females cannot avoid.


  • Ecology


  • ISSN: 1365-2435
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