Patterns and drivers of beta diversity in bird communities associated with blue-green infrastructure in rapidly urbanizing landscapes

Habitat loss driven by land-use change is a major factor shaping the dynamics of urban bird community structures. However, the potential mechanisms by which the spatial configuration and composition of blue-green infrastructure, recognized as biodiversity hotspots in urban landscapes, influence urban bird beta diversity remain insufficiently understood. This study was conducted in the built-up area of Yinchuan, an internationally recognized wetland city in Northwest China. From December 2023 to June 2024, we systematically surveyed bird communities during both the breeding and wintering periods across 29 blue-green space mosaics. We quantified taxonomic, functional, and phylogenetic beta diversity, along with their turnover component and nestedness-resultant component, based on both pairwise beta diversity and multiple-site beta diversity. We further assessed the relative importance of landscape variables and spatial geographic distance in shaping beta diversity patterns and used hierarchical modeling of species communities (HMSC) to explore the responses of bird occurrence and functional traits to landscape variables. Our results revealed that species turnover was the dominant driver of taxonomic, functional, and phylogenetic beta diversity. Seasonal differences were observed in the effects of spatial geographic distance and landscape structure on beta diversity and its components, with landscape variables showing higher explanatory power than geographic isolation. In the breeding period, landscape diversity and waterbody area had positive effects on bird occurrence, whereas in the wintering period, most landscape features—except for landscape diversity—exerted neutral or negative influences. Regarding functional traits, we found that reproductive traits, flight ability, and foraging characteristics responded significantly to landscape structure, and that some small-bodied species active in aerial and canopy layers were more adaptable to habitat fragmentation. This study provides novel insights into the assembly processes and driving mechanisms of urban bird communities and offers scientific support for the notion that designing and maintaining blue-green infrastructure can contribute to urban biodiversity conservation.