Carotenoid-based ornamentation and status signaling in the house finch |
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Authors: | McGraw Kevin J; Hill Geoffrey E |
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Institution: | Department of Biological Sciences and Alabama Agricultural Experiment
Station, 331 Funchess Hall, Auburn University, Auburn, AL 36849-5414,
USA |
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Abstract: | The status signaling hypothesis (SSH) was devised primarilyto explain the adaptive significance of avian ornamental colorationduring the nonbreeding season. It proposes that conspicuousmale plumage serves as an honest signal of social status withina population of birds. However, to date this hypothesis hasbeen well tested and supported for only one type of plumage
coloration, melanin-based coloration. Carotenoid-based pigmentationis known to positively reveal male health and condition duringmolt in a variety of species, but it is poorly understood whetherthis ornament type can also function as a status signal duringthe winter. We tested the SSH in male house finches (Carpodacusmexicanus) by manipulating the carotenoid-based plumage brightnessof first-year males and then pairing unfamiliar birds of differingcoloration in a series of dominance trials in captivity. Manipulated
plumage color was unrelated to win/loss outcome in these trials.Similarly, the natural pigmentation of males was a poor predictorof winter dominance; as in other studies with this species,we found only a weak tendency for naturally drab males to dominatenaturally bright males. These results suggest that carotenoid-basedcoloration is not a reliable indicator of social status inmale house finches during the nonbreeding season. In fact, carotenoid-based
coloration may function only in mate choice in this species,and it may be retained throughout the year either because timeconstraints preclude a second plumage molt or because it aidsin pair formation that begins in late winter. |
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Keywords: | aggression dominance Carpodacus mexicanus carotenoids house finches plumage coloration |
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