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Science 4 April 2003:
Vol. 300. no. 5616, p. 13
DOI: 10.1126/science.300.5616.13g
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Mate choice is frequently influenced by physical cues, which are used to indicate general vigor to prospective partners, but such secondary sexual traits can impose a cost. Faivre et al. (p. 103) find a trade-off between the role of carotenoids in bill coloration and immune responses. In male blackbirds, where bright orange bills are preferred by females, activation of the immune system diminished bill color intensity by depleting carotenoids from keratin. Bill coloration is a secondary sexual trait in zebra finches, too, and Blount et al. (p. 125; see the news story by Pennisi) observe that more intense coloration produced by supplementing dietary carotenoids correlated with preferred selection by females and with increased immune response.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)