Investigating the effects of three-dimensional building morphology on urban bird diversity: Evidence from 77 cities in China

Urban buildings profoundly and complexly influence bird diversity. While previous studies have investigated the effects of building cover and building height on bird diversity within individual cities, much less attention has been given to building height heterogeneity, and the combined effects of these three-dimensional building morphology features at broader spatial scales. Using the urban areas of 77 Chinese prefecture-level cities as sample units and citizen science bird observations collected between 2017 and 2023, we applied the Mann–Whitney U test, eXtreme Gradient Boosting regression model, and the SHapley Additive exPlanation method to explore the effects of building cover, building height, and building height heterogeneity within urban areas on bird species richness. Our results show that the urban three-dimensional building morphology features—particularly the building height heterogeneity—are key explanatory variables for bird species richness. The heterogeneity of building heights is positively associated with bird occurrences in urban areas and urban bird species richness. Thus, the development of bird-friendly cities should explicitly incorporate vertical building morphology features into urban planning and design, including the protection of vertical bird habitats by vertical greening systems and the construction of bird flight corridors by regulations that ensure graduated building heights.