In this study we evaluated the bird species composition in three structurally different forest environments in the Natural Park of Sertão (NPS) and its surroundings, in the southern limit of the Atlantic Forest, Brazil. The assemblage patterns found can be explained by the ecological traits and the sensitivity levels of birds to forest fragmentation, which in turn seem to reflect different forest structures in the NPS and its surroundings. Although the Edge and Buffer areas have greater diversity, the Core areas showed great importance in maintaining species that are more sensitive to forest fragmentation. For conservation of bird fauna in the NPS, the maintenance of the core areas is essential, especially for those species that require a structurally preserved environment.