Drivers of taxonomic, phylogenetic, and functional diversity of waterbirds in urban wetlands.

Urban wetlands are considered as "habitat islands" within the urban matrix that contribute to species conservation. Waterbirds are sensitive pollution indicators in terrestrial and aquatic ecosystems, and their diversity in urban wetlands reflects the response of wildlife to urbanization. However, very few studies have investigated seasonal differences in the multidimensional diversity of waterbirds in urbanized landscapes. In this study, we analyzed various wetland parameters that could potentially affect the seasonal variations in multidimensional diversity of waterbirds in Nanjing, China. We surveyed waterbirds in 29 urban wetlands using the point count method during breeding and non-breeding seasons from November 2022 to June 2023. We then employed multiple linear regressions and information-theoretic approaches to investigate the impact of wetland characteristics on waterbird diversity. We found that water body area and buffer zone connectivity consistently emerged as positive factors affecting waterbird taxonomic and phylogenetic diversity across seasons. Conversely, the urbanization synthetic index was negatively correlated with waterbird diversity only during the breeding season. Regarding functional diversity, we found that the positive correlation between buffer zone connectivity and waterbird diversity was specific to the breeding season. Therefore, for effective conservation of waterbird diversity in our system, wetland planning should prioritize expanding wetland water body areas, enhancing wetland connectivity, minimizing human disturbance during the breeding season, and implementing ecological restoration measures in urbanized wetlands to mitigate adverse effects of urbanization.