Precipitation is the dominant driver for bird species richness, phylogenetic and functional structure in university campuses in northern China

Background Although urbanization is threatening biodiversity worldwide, the increasing green urban spaces could harbor relatively high biodiversity. Therefore, how to maintain the biodiversity in urban ecosystem is crucial for sustainable urban planning and management, especially in arid and semiarid regions with relatively fragile environment and low biodiversity. Here, for the first time we linked species richness, phylogenetic and functional structure of bird assemblages in university campuses in northern China with plant species richness, glacial-interglacial climate change, contemporary climate, and anthropogenic factors to compare their relative roles in shaping urban bird diversity. Methods Bird surveys were conducted in 20 university campuses across Inner Mongolia, China. Ordinary least squares models and simultaneous autoregressive models were used to assess the relationships between bird species richness, phylogenetic and functional structure with environmental factors. Structural equation models were used to capture the direct and indirect effects of these factors on the three components of bird diversity. Results Single-variable simultaneous autoregressive models showed that mean annual precipitation was consistently a significant driver for bird species richness, phylogenetic and functional structure. Meanwhile, mean annual temperature and plant species richness were also significant predictors for bird species richness. Conclusions This study suggests that campuses with warmer and wetter climate as well as more woody plant species could harbor more bird species. In addition, wetter campuses tended to sustain over-dispersed phylogenetic and functional structure. Our findings emphasize the dominant effect of precipitation on bird diversity distribution in this arid and semiarid region, even in the urban ecosystem.