Abstract Adkins-Regan 9514088 The goal of the proposed research is to analyze developmental processes leading to adult mate choice and mate preferences, especially preferences that are sexually dimorphic (different in males and females). The project will focus on a particularly robust and widespread aspect of mate choice, preference for opposite-sex partners (sexual partner preference), and a species well-suited to the goal, the zebra finches treated with estrogen during the first two weeks posthatch and housed in an all-female zebra finches treated with estrogen during the first two weeks posthatch and housed in an all-female environment from 40 days (independence from the parents)to 100 days (young adulthood) then prefer to pair with other females. In order to address important questions raised by this discovery, a series of experiments will be conducted in which annals are exposed to different hormonal or social environment manipulations during development and then tested for sexual partner preference--organizational effects of hormones produce early in development, and sexual imprinting--and will elucidate the manner in which hormonal and experiential influences interact during development. This work will advance our understanding of mate choice and of reproductive behavior development.