Integrity and Size of Green Spaces Are Critical for the Functional Diversity of Birds: Evidence from the Eastern and Northwestern Regions of China

Urbanization often changes bird species richness and affects the functional diversity. Therefore, understanding these changes helps city planners improve green space design and land use planning. Our study used multiple datasets to explore the effects of landscape patterns and natural environments on the functional diversity of birds in urban parks and campuses in the eastern and northwestern regions of China. Firstly, we used the data to calculate birds of the functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv) of 68 urban spaces in the eastern and northwestern regions of China. Further, we established generalized linear models of natural factors, human factors, and functional diversity. Results showed more bird species with unique traits were in the northwestern region. This may be because the earlier urbanization in the eastern region filtered out urban-sensitive species, leaving behind urban adapters. Moreover, we found that the fractal dimension index was the most significant positive factor of FRic in the eastern region but the most significant negative factor of FDiv. Elevation was the most significant negative influence factor of FEve in the eastern region, but it was the most potent positive influence factor of FRic in the northwestern region. Population density had a significant positive effect on FDiv in the northwestern region. However, green space areas significantly negatively impacted FEve in the northwestern region. In addition, birds in parks in both regions had more functional traits than those on campuses, possibly because of the larger green space in parks, which may contain more fragments of native vegetation and reduce human interference. Our study suggests that preserving more original vegetation and reducing human disturbance in cities can increase the functional diversity of urban birds and improve urban ecosystem functions.