Urbanization and climate drive long-term bird community trends across a desert city ecosystem.

Sustaining biodiversity requires measuring the interacting spatial and temporal processes by which environmental factors shape wildlife community assembly. Declines in bird communities due to urban development and changing climate conditions are widely documented. However, the combined impacts of multiple environmental stressors on biodiversity remain unclear, especially in urbanized desert ecosystems. This is largely due to a lack of data at the scales necessary for predicting the consequences of environmental change for diverse species and functional groups, particularly those that provide ecosystem services such as seed dispersal, pest control, and pollination. Trends in the prevalence and diversity of different functional groups contribute to understanding how changes in bird communities impact well-being through the lens of ecosystem services. Across the rapidly developing drylands of the metropolitan Phoenix, Arizona, USA, we ask the following question: How have inter- and intra-annual landscape changes associated with urbanization and climate shaped the dynamic characteristics of bird communities, specifically the abundance and richness of species and their functional groups? We analyzed long-term drivers of bird communities by combining a two-decade, multi-season spatial dataset of environmental conditions (urbanization, vegetation, temperature, etc.) with biotic data (species richness and abundance) collected seasonally during the same time periods (winter and spring; 2001-2016). Results show that increased impervious surface area and land surface temperature were negatively associated with overall bird abundance and species richness across the study period, especially during winter. However, these relationships varied among functional groups, with potentially mixed outcomes for ecosystem services and disservices provided by urban biodiversity. By improving knowledge of long-term trends in multiple environmental drivers that shape wildlife community dynamics, these results facilitate effective evaluation of how landscape management practices in drylands influence the outcomes of evolving human-wildlife relationships.