Effects of urbanization and vegetation on bird diversity in a megacity of central China

Species decline and community structure disruption of urban forest patches have been widely considered, but their mechanisms underlying rapid urbanization have not been fully studied. Here, a 3-year investigation of birds was conducted in 30 forest patches along an urban-suburban gradient of Wuhan, a rapidly urbanizing megacity in central China. Effects of urbanization and vegetation on the taxonomic, functional, and phylogenetic diversities of specialists, generalists, and total birds were separately tested. The results showed that the taxonomic diversity of total birds and generalists increased with habitat complexity, and remained highest with a moderate degree of urbanization, while that of specialists increased with increasing patch area size. Functional diversity of total birds and generalists increased with increasing habitat complexity and proportion of fruity plants and rapidly increased when patch area exceeded a threshold (c.a., 80 ha), whereas that of specialists positively correlated with the proportion of fruity plants. Phylogenetic diversities of all three groups of birds were positively correlated to habitat complexity and proportion of fruity plants, and generalists increased with plant diversity and rapidly increased when patch area exceeded the same threshold. These results suggest that high habitat complexity and moderate urbanization could maintain a high diversity of birds, and there was a small-island effect of patch area on bird diversity. Specialists were more dependent on fruity plants and more sensitive to urbanization. To sustain bird diversity, moderate urbanization, threshold of patch area, vegetation complexity and abundance of fruity plants should be integrated into urban forest planning and ecological-based management.