How urban impervious surface shapes bird foraging behavior in an arid city

Wildlife behavior and interactions in urban ecosystems can vary across landscape types and species, with some birds dominating human-derived resources. This study investigates the relationship between urbanization, measured as impervious surface cover, and bird foraging behavior in the Phoenix metropolitan area in Arizona, USA. We conducted 126 feeding trials across 13 sites along a gradient of urbanization and bird interactions with anthropogenic food sources present. Trials were conducted using popcorn placed at random distances and orientations from a trash can. We recorded bird species visiting feeding stations and time to first visit during 20-minute trials and then quantified relationships among visitation timing (latency), species richness, and impervious surface coverage. Time to first visit was negatively correlated with the amount of impervious surface, with the highly urban areas having birds arrive at the feeding station the soonest. Great-tailed Grackles (Quiscalus mexicanus) comprised the most common visitor across all impervious surface levels. Non-native doves like Rock Pigeons (Columbia livia) and Eurasian Collared-doves (Streptopelia decaocto) were quicker to visit feeding stations compared to native doves like Mourning Doves (Zenaida macroura), Inca doves (Columbina inca), and White-winged Doves (Z. asiatica). Small urban-adapted generalists, like House Sparrows (Passer domesticus) and House Finches (Haemorhous mexicanus), tended to be more frequent visitors at highly urbanized sites compared to larger birds. These emphasize how species-specific foraging behaviors can differentiate resource use by birds in urban areas.