Artificial light at night as a driver of urban colonization by an avian predator

Abstract

Context: Urbanization and artificial light at night (ALAN) are major drivers of local biodiversity losses causing community alterations, disruption of predator-prey interactions, and ultimately, promotion of cascading effects. However, some species can colonize urban environments. Objectives: We explore the role of ALAN as a driver of the colonization of urban environments by a nocturnal avian predator, the burrowing owl Athene cunicularia. Methods: We studied in a suburban locality in La Pampa, Argentina: (1) prey availability with pitfall traps under streetlights and control sites; (2) diet by analyzing pellets; (3) space use by deploying GPS data-loggers to breeding owls; (4) nesting habitat selection by comparing environmental variables at nest and random locations; and (5) productivity by correlating environmental variables with the number of fledglings. Results: First, streetlights altered the invertebrate availability, attracting them to illuminated areas. Second, the owl diet was more similar to the invertebrate taxa trapped at pitfall traps under streetlights than that in control traps. Third, owl space use was determined by streetlights. Owls spent more time around light sources, particularly during the nighttime. Fourth, the most important habitat feature influencing the nesting habitat selection was the distance to streetlight. Owls selected areas close to streetlights for nesting. Finally, productivity was not explained by any of our habitat variables. Conclusions: We demonstrate that ALAN alters the availability of invertebrates and plays a role in the diet, space use, and occupation of urban burrowing owls. Streetlights increase foraging efficiency for owls due to the clumping of prey attracted to lights. This predator-prey relationship might be only supported in suburban environments where low urbanization levels let burrowing owls nest in bare ground areas, and invertebrates are attracted to ALAN from surrounding wilder areas.