My thesis research explored the role of female coloration in eastern bluebirds (Sialia sialis). Female eastern bluebirds are drabber than their male counterparts, but they possess bright plumage on their rump and tail that might act as a sexual signal. Studying eastern bluebirds in the wild, I discovered that females with brighter plumage had a higher reproductive success, measured as the number and condition of nestlings, than females with duller plumage. However, males showed no preference for brighter females in an aviary mate preference experiment. Consequently, male mate preference does not appear to be driving or maintaining the variation in female coloration; and presumably, males are not using female coloration for mate choice. Alternatively, female coloration may be important in intrasexual (female-female) competition.