CAREER: Song and Plumage in the House Finch: A Study of Signal Content in a Multiple-Signal System

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IBN-9722171 Hill Bright colors and beautiful song are among the most conspicuous features of birds, but these traits pose a paradox for evolutionary biologists. How could such gaudy traits, which seem to waste energy and expose individuals to predators, have evolved by natural selection, a process that should promote survivorship and reproduction? The generally accepted answer to this question is that such ornamental traits arose through sexual selection, a process that promotes access to mates either through mate attraction or mate defense. Female mate choice has been shown to be an important selective agent in the evolution of ornamental traits, but why should females choose such traits? One explanation for this riddle is that ornamental traits serve as honest signals of male quality. By choosing males with well-developed ornaments, females choose better-than-average males. The plot thickens further, though, in that most species of animals have not one but multiple ornamental traits. For instance, most species of songbirds have both colorful plumage and song. This research will study the function of song and colorful plumage in the House Finch, a common backyard bird found throughout the contintental U.S. Studies will test the idea that female House Finches gain different information about male quality from different ornamental traits. Colorful plumage in the House Finch is a result of carotenoid pigments, which birds must obtain from their diet. Thus, plumage brightness is a function of the nutritional condition of males at the time when feathers are grown. The control of song development is less well understood, but it may also be dependent on nutrition. The focus of this work is on two measures of male quality: disease resistance and parental effort. Using a combination of experiments conducted with captive birds and observations of wild birds, the study will determine how song and ornamental plumage coloration of male House Finches relate to two different types of disease: coccidia, a chronic intestinal parasite, and conjunctivitis, a bacterial infection of the eye and upper respiratory system with rapid onset. The prediction is that song, which is produced at the time of display, will be a better indicator of fast- acting disease of short duration. In contrast, plumage, which is grown over a six-week period, months before it is used in display, will be a better predictor of chronic infection. Song and plumage may also convey different information about the ability of males to provision young. This research will be among the first to simultaneously investigate the function of multiple ornamental traits, and will provide new insight into the process of sexual selection and the evolution of ornamental traits in animals. The idea that conspicuous ornamental traits in male animals might convey information about prospective mates to females is an intuitively appealing hypothesis that many students (in the broad sense - including high school students, science teachers, undergraduates and adult education students) find compelling. The research project will incorporate an educational focus involving participation by the previously-mentioned student populations. The House Finch is an ideal species for studies intended to introduce students to field biology - they are small, docile, easy to catch, have bright colors that are easy to quantify, are habituated to people, and nest in conspicuous locations on campus. In addition, House Finches are found in nearly every schoolyard in the U.S., and part of this study will also develop science exercises with high school teachers, and allow students to experience the challenge and excitement of real scientific investigation.