Overwinter roost activity patterns in response to environmental conditions along a rural-urban gradient

Abstract

1. Organisms rely on environmental cues, such as moonlight illumination and weather, to modulate nocturnal behaviors that reduce predation risk and conserve energy during demanding periods. Urbanization can alter the reliability of cues, potentially impairing organisms' ability to respond appropriately with consequences in increasingly urbanized landscapes. 2. We leveraged the Motus Wildlife Tracking System to identify roost initiation, roost departure and nocturnal restlessness of dark-eyed juncos (Junco hyemalis) overwintering along an urban to rural gradient to determine if activity patterns are affected by weather, moonlight illumination, and urbanization. 3. Nocturnal behavior of overwintering juncos varied with environmental factors, including moonlight illumination and temperature. However, the strength of these responses differed among sites, suggesting that natural cues of moonlight illumination were masked in urban areas, where individuals were more responsive to temperature. 4. Our results suggest that urbanization weakens birds' responsiveness to natural light cues, likely because artificial lighting reduces the visibility of moonlight; representing a key mechanism by which human-altered landscapes can disrupt nocturnal ecology in birds.