Two recent studies have shown that sites in southeastern Arizona support large numbers of hummingbirds, particularly during southbound migration. Results from HMN's monitoring work in southeastern Arizona suggest that the Madrean pine-oak woodlands support the largest number of hummingbird species in the Sonoran Joint Venture region. However, little is known about habitat requirements for nesting and long-term reproductive success of most hummingbird species. This project will increase knowledge of habitat requirements of hummingbirds in this little-known and very important habitat. The Hummingbird Monitoring Network and the Southwestern Research Station in the Chiricahua Mountains are developing a partnership to study habitat requirements for successful nesting of hummingbird species in the Madrean pine-oak woodlands. Over the course of this project we will (1) determine if there are specific habitat requirements for nesting of hummingbird species in this zone; (2) determine if grazing alters the habitat sufficiently to effect change in nesting success; (3) determine the best long-term monitoring sites for all North American hummingbirds; and (4) estimate abundance so trends in populations can be detected.