Seasonal Use of Habitat by Shrub-Breeding Birds in a Southeastern National Forest

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Populations of shrub-breeding birds are declining in eastern North America, and loss of habitat has been implicated in these declines. Seasonal use of habitat by shrub-breeding birds in the southeastern US remains understudied despite the fact that it is well documented that species resident within a region can shift habitat use dramatically between seasons. To better understand year-round habitat occupancy by shrub-breeding birds, we conducted bird counts and vegetation surveys during summer and winter 2008–2009 within Tuskegee National Forest, Alabama. We used multi-season occupancy models to examine use of habitat and to contrast seasonal occupancy patterns of four species of resident shrub-breeding birds—Brown Thrashers (Toxostoma rufum), Eastern Towhees (Pipilo erythrophthalmus), Northern Cardinals (Cardinalis cardinalis) and Carolina Wrens (Thryothorus ludovicianus). Brown Thrashers and Eastern Towhees are partially migratory—meaning some populations have separate breeding and wintering areas—whereas Carolina Wrens and Northern Cardinals are non-migratory. All four species showed seasonal changes in use of habitat between summer and winter, and all species were associated with both vegetation structure and certain types of cover. Further, partially migratory shrub-breeding species had greater site-turnover and increases in occupancy between summer and winter than non-migratory species. Our results suggest that: (1) management actions based on breeding habitat requirements will likely not create suitable winter habitat, and (2) management of resident shrub-breeding birds will require not only the creation and maintenance of certain types of cover, but also certain structural aspects of vegetation within habitats.