The Atlantic Forest is one of the most threatened biodiversity hotspots in the world due to habitat fragmentation. Restoration and connectivity of forest fragments are crucial to maintain viable populations of forest-dependent species. During winter and summer, we studied the bird diversity, its components and composition (including specialist and generalist species) in three different vegetation types: mature forest (MF), secondary forest (SF) and grassland (G) of an ecological corridor in Misiones, Argentina. We determined the influence of alpha diversity (of each habitat) and beta diversity (species turnover between habitats) on gamma diversity (regional diversity in the corridor), to provide conservation management recommendations. MF showed the highest values of bird diversity, richness, evenness and abundance, followed by SF and G, in both seasons. Only MF showed a possible seasonal variation in diversity and richness. The species composition of SF was similar to MF. However, G, where pasture specialist and edge species were the most common species recorded (70% of its avifauna), had very low similarity to MF, where the most forest specialist species were found (53%). As alpha diversities were higher than beta values, the bird diversity in the studied corridor mainly resulted from the diversity in each vegetation type, in both studied seasons. We therefore recommend preservation of both MF and recovering SF due to their high bird diversity and the presence of forest-dependent, threatened and endemic bird species. We also urge the creation of ecological corridors between protected forest remnants of the Atlantic Forest.
