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EFFECTS OF EXOGENOUS ESTROGEN ON MATE SELECTION OF HOUSE FINCHES
Clark, J., A Fairbrother, L. Brewer, H. McQuillen, AND R S. Bennett. EFFECTS OF EXOGENOUS ESTROGEN ON MATE SELECTION OF HOUSE FINCHES. Presented at 21st SETAC Annual Meeting, Nashville, TN, November 12-16, 2000.
Concern about the potential for endocrine disrupting chemicals to interfere with normal breeding behaviors of wildlife has prompted this study of effects of exogenous estrogen on mate selection in songbirds. The house finch (Carpodacus mexicanus) was selected as a model as it is ubiquitous in the US and previous investigators have reported that male plumage coloration is important in mate attraction. Plumage color is determined during the fall molt and is a function of both caratinoid concentration in food and testosterone levels in the males. Females have been shown to prefer the red color morph in preference to birds with orange or yellow plumage on head and rump. While exposure to estrogenic substances during mate selection times of early spring will not influence plumage coloration, it may alter either the female's ability to discriminate among potential mates or change aspects of male behaviors that also influence mate selection. This study placed a single female into a test chamber where she could visually access two males, although not simultaneously. The amount of time she spent with each male was recorded. Three females were tested with pairs of males representing choices between red, orange, yellow, and dull (no color) plumage. Tests were repeated with females dosed with a continuous-release estrogen pellet that delivered 25 mg of estradiol-17b over 21-days during the mate selection period. The same sequence of tests was conducted with males implanted with the estadiol pellets. Elevation of estrogen levels was verified through measurement of estrone conjugate excreded in fecal/urates. Results of undosed birds showed the expected pattern of females preferring red males and being less discriminating among other colors. Effects of elevated estrogen levels on mate selection will be discussed. This study demonstrated that the house finch is a suitable model for studying - - -