Relationships among survival, body condition, and habitat of breeding Swainson's Warblers

For migratory birds, the selection of high-quality breeding and nonbreeding habitats has significant implications for fitness. One potential reflection of habitat quality is body condition. Condition may influence adults' survival, a key demographic variable for population growth. Access to abundant resources should lead to good condition and birds maintaining or improving their condition over time. As many species use multiple habitats, recognizing the relative quality of these alternative environments is important for understanding population dynamics and aiding conservation. One species that uses a range of habitats is Swainson's Warbler (Limnothlypis swainsonii), a species of conservation concern that breeds in the southeastern U.S. from 2004 through 2007, we studied survival and body condition of Swainson's Warblers at three sites in eastern Arkansas, two dominated by mature forest, and one in an industrial forest managed for timber production. Birds in better condition at initial capture survived at a higher rate at two of three locations. moreover, at all sites the birds' body condition improved through the breeding season and varied little by site. Body condition was positively related to dense understory vegetation and negatively related to herbaceous ground cover. Our results suggest that both mature and industrial forests may provide adequate habitat for Swainson's Warbler. Because of the relationship between body condition and survival, the observed habitat-related differences in body condition have implications for habitat quality. To provide high-quality habitat for Swainson's Warbler, management should focus on providing forests with dense understory vegetation and, to facilitate efficient foraging, little herbaceous ground cover.