Environmental changes resulting from forest succession process may lead to changes in the abundance and composition of species. In each successional stage, faunal composition will depend on the structure of the habitats and the ecological requirements of each species. The effects seem to be more evident in small isolated forest fragments. In this study we recorded bird species composition and richness at different stages of secondary forest in a protected area located in a highly-fragmented region in southern Brazil. We predicted that bird species composition and richness will change according to the secondary forest stage, and will be affected by the ecological requirements of species. The study was carried out in the Mata do Rio Uruguai Teixeira Soares Municipal Park (TSP), in the northern part of the state of Rio Grande do Sul, Brazil. The park is the largest protected area in the region, with 423 ha. Representative areas of the three successional stages of secondary forest within TSP were selected, and the bird species in each area were recorded using the counting point sampling method. A total of 145 bird species were recorded in the three areas. There were differences in species composition between the areas, indicating that the structure of the bird community is directly linked to successional stages. This relationship is improved by differences in the number of birds with certain ecological traits between the areas. The size, connectivity of the forest fragments and the availability of habitats may be affecting the distribution of the avifauna in the park. Changes in the landscape may promote a restructuring of avifaunal communities, where species with certain ecological traits can be favored or excluded. The TSP, although relatively small, is important for the maintenance of bird species because it is a rare, well-preserved fragmented of the deciduous seasonal forest in the region.