Urbanization is associated with unique community simplification among birds in a neotropical landscape

Context Conversion of land cover by urban expansion is typically thought to reduce functional diversity by homogenizing species composition, at least in well-studied temperate locations. Studies of highly diverse and disturbance-sensitive tropical ecosystems remain rare. Objectives By exhaustively surveying resident forest bird communities across an urbanizing Neotropical region we aimed to: (1) assess the patterns and landscape-level correlates of species occurrences in forest habitat; (2) identify trait predictors of species occurrences in urban forest patches; and (3) evaluate the associations between urbanization and phylogenetic and functional diversity. Methods We inventoried forest bird communities along the Panama Canal, an area characterized by a strong urbanization gradient from remnant patches surrounded by a densely populated metropolis (Panama City) to extensive tracts of protected rainforest in National Parks. We determined associations of community composition, species traits, and functional and phylogenetic diversity with landscape-level attributes. Results In contrast to most previous studies reporting community homogenization, forest patches in urbanized central Panama contained different subsets of resident bird species. Species in forests within in the most urbanized subregions generally were those with strong dispersal abilities, short developmental periods, and recent evolutionary histories. Although species identities varied among urban patches, functional and phylogenetic diversity were similar. Conclusions Our results are best characterized by community “simplification”—a loss of species without loss of functional or phylogenetic representation. The dissimilarity of bird community composition among forest patches in urbanized regions appears to be a unique outcome and could be influenced by patch-specific attributes.