Garden Warbler Emphasis Type="Italic"Sylvia bor

Authors: Carlo Catoni Benjamin Metzger H Martin Schaefer Franz Bairlein

Publish Date: 2010/07/17

Volume: 152, Issue: 1, Pages: 153-159

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Abstract

The concept of optimal foraging has been used to show how animals can increase their fitness by actively regulating the ingestion of nutrients or by avoiding detrimental plant metabolites such as alkaloids There is however considerably less information available on whether and if so how animals actively select beneficial secondary compounds such as dietary antioxidants In the last two decades carotenoids have been the most intensively studied dietary antioxidants in behavioural ecology and the expression of carotenoidbased ornamentation has become a model for studying the condition dependence of sexually selected traits In a series of experiments in which we offered individual Garden Warblers Sylvia borin a choice between two foods one with and one without carotenoids we found that individual birds did not select food for the maximum amount of carotenoids rather they choose for a highly consistent carotenoid intake during the course of different dualchoice experiments in which the food offered differed in carotenoid content However it remains unclear whether the individual birds were able to optimise their carotenoid intake and therefore the expression of life history traits—even though individuals differed consistently in their carotenoid intake In particular females tended to avoid food with high carotenoid contents Based upon the highly consistent carotenoid intake of individual birds we conclude that our birds were able to perceive the presence of carotenoids in the food without the use of visual cues We suggest that these results may shed new light on the mechanisms that birds may use to regulate the ingestion of these antioxidants and consequently possibly affect the expression of life history traits such as immunocompetence or sexually selected traitsWe are grateful to Ulrike Strauss and Adolf Völk for assistance in bird maintenance We also gratefully acknowledge support by the DAAD to CC A/06/12402 and DFG to HMS Scha 1008/41 to BM BA816/18–1 The experiments comply with the current laws of Germany in terms of animal health and care

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