Carotenoid Composition of Invertebrates Consumed by Two Insectivorous Bird Species
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Dietary carotenoids are important pigments, antioxidants, and immune-stimulants for birds. Despite recent interest in carotenoids in bird ecology, we know surprisingly little about the carotenoid content of invertebrates consumed by birds. We compared carotenoid (lutein, β-carotene, and total) concentrations in invertebrates brought to nestlings by two insectivorous passerines, the great tit, Parus major and the pied flycatcher, Ficedula hypoleuca. We also compared carotenoid levels between environments that were either polluted by heavy metals or were not polluted, because the carotenoid-based plumage color of P. major nestlings is affected by environmental pollution. Lepidopterans were the most carotenoid-rich food items and contained the largest proportion of lutein. There were no differences in carotenoid concentrations in the food items of the two bird species but P. major nestlings obtained more carotenoids from their invertebrate diet than F. hypoleuca nestlings because the P. major diet had a higher proportion of lepidopteran larvae. In polluted areas, P. major nestlings consumed lower levels of dietary carotenoids than in unpolluted areas because of temporal differences in caterpillar abundance between polluted and unpolluted sites. Our study suggests that pollution-related difference in nestling plumage color in P. major is related to varying dietary proportion of lutein-rich food items rather than pollution-related variation in insect carotenoid levels.
Key WordsCarotenoids Caterpillars Insects Invertebrates Lutein Terrestrial food chain
We thank Jorma Nurmi, Mari Ryömä, and Janne Riihimäki for participating in field work, and Terhi Sundman for help in carotenoid analyses. Anssi Teräs, Antti Haarto, Seppo Koponen, Veikko Rinne, Kai Ruohomäki, Ilari Sääksjärvi, and Jouni Sorvari identified the invertebrate samples. Eric Le Tortorec revised the English in the manuscript. Two anonymous referees gave valuable comments on the manuscript. This study was financially supported by the Academy of Finland (TE: project number 8119367) and Finnish Cultural Foundation (SH).
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