Urban greenspace drivers of bird species richness differ between migratory and resident species across the full-annual cycle

Levi P Hoskins, Brittany M. Mason, Benjamin Baiser , Corey T. Callaghan 

Urban greenspaces are increasingly under pressure from urbanization. Greenspaces provide some of the last remaining resources for biodiversity in cities, but their ecological value varies substantially among sites. Despite their importance, we still lack a comprehensive understanding of which urban greenspaces species use across the full-annual cycle and among migratory groupings. To investigate this, we assessed the impact of area, isolation, and urbanization intensity on occupancy by migratory and resident bird species in urban greenspaces across their full-annual cycle. We aggregated community science data from eBird for 66 urban greenspaces across Broward, Miami-Dade, and Palm Beach Counties in South Florida, USA. Data were selected via spatial filtering and the integration of eBird checklists from 2010 to 2024. Our analyses included 366 bird species, classified as migratory or resident. To assess the influence of the 3 greenspace attributes on avian species richness, we fit generalized linear mixed models. We found that migratory and resident species richness were differentially impacted throughout the full-annual cycle by greenspace attributes. Resident species were more likely to be found in more urbanized regions, whereas migratory species were more likely to avoid these areas. However, both groups declined in richness the more isolated a greenspace was, and this effect was more pronounced for residents. Species richness across all species increased with area. We showed that area, isolation, and level of urbanization impacted overall species richness but were moderated by seasons and migratory status. Understanding these fundamental differences is increasingly important for managers of greenspaces to curate areas that benefit avian species with different life-history traits throughout the year.