I study social behaviors in wildlife vertebrates, concentrating on steroid hormones in order to evaluate the proximate mechanisms and functions of the behaviors. Changes in steroid hormones concentrations and associated behavioral changes can provide valuable information on the well being of individuals, groups, and populations. We integrate data on stress and sex steroid hormone concentrations that are sampled non-invasively from wildlife, with data on affiliative, aggressive, parental, and display behaviors, in order to study questions in behavioral ecology. Our study takes place in the field, under natural conditions, and since it often uses long-term study systems, can detect trends, including the impact of human disturbances. We use non-invasive techniques for hormone and genetic testing. Hair has proven to be an informative matrix for studying baseline steroid concentrations. Feathers, although offering a more limited time frame, is a promising matrix as well. We are currently exploring other species-specific matrices that may advance the field of behavioral endocrinology by providing unhampered wildlife samples, which will be used to increase our understanding of mechanisms under natural contexts. I am especially interested in trade-offs between the functional attributes of stress and sex steroids and costs associated with their circulation, in the context of sex, identity, life-history theory, reproductive success, and survival.