Long-term effects of yolk androgens on phenotype and parental feeding behavior in a wild passerine
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Early growth conditions, such as exposure to maternally derived androgens in bird eggs, have been shown to shape offspring in ways that may have important long-term consequences for phenotype and behavior. Using an experimental approach, we studied the long-term effects of yolk androgens on several phenotypic traits and parental behavior in adult and female collared flycatchers (Ficedula albicollis). We elevated yolk androgen levels and monitored the experimental recruits the following breeding seasons. Androgen treatment had a sex-dependent effect on adult body condition, yolk androgen-treated males being heavier than control males when controlling for size, a result which may be caused potentially by selective mortality, physiological differences, or different life-history strategies. Androgen treatment did not however affect the expression of sexually selected plumage ornaments (forehead and wing patch size), UV coloration, or parental feeding rate in either sex. Our results suggest that yolk androgens are unlikely to affect sexual selection via plumage characteristics or contribute to breeding success via altered parental care. Yolk androgens do not seem to act as a means for female collared flycatchers to enhance the attractiveness of their sons. The lower return rate previously observed for androgen-treated male offspring compared to controls may therefore not be due to lower mating or breeding success, but may rather reflect lower survival or higher dispersal propensity of yolk androgen-treated males.
KeywordsMaternal effect Testosterone Bird Plumage trait Sexual selection
This study was financially supported by Turku University foundation, Finnish Cultural foundation (grants to S.R.), Emil Aaltonen Foundation (a grant to T.L.), the ANR (Agence Nationale de la Recherche—grant ANR-06-JCJC0082 to B.D.), the CNRS (Centre National de la Recherche Scientifique—PICS grants to B.D.) and the Swedish Research Council (grants to L.G.). We thank Maaike de Heij, Tuomo Jaakkonen, Melissa Lemoine, Christoph Meier and all the field assistants, especially Lise Duconte, Laure Cauchard, and Laurent Brucy, for help in collecting the data.
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