Light pollution prolongs avian activity

Light pollution disrupts light–dark cues that organisms use as timetables for life. Although studies—typically focusing on individual species—have documented earlier morning onset of bird vocalization in light-polluted landscapes, a synthesis of light pollution effects across species, space, and season is lacking. We used a global acoustic dataset of more than 60 million detections, representing 583 diurnal bird species, to synthesize effects of light pollution on avian vocalization. On average, light pollution prolonged vocal activity by 50 min. Light pollution responses were strongest for species with large eyes, open nests, migratory habits, and large ranges and during the breeding season. Prolonged activity may confer negative, neutral, or positive fitness effects; documenting these fitness effects and curbing light pollution are challenges for 21st-century conservation.