Does artificial light at night (ALAN) affect foraging behavior and corticosterone release in barn owls?

With global human population growth, anthropogenic pollution has intensified, including the rapid expansion of artificial light at night. As an environmental stressor, artificial light at night has been shown to disrupt behavioral and physiological processes across a wide range of species. However, its impact on nocturnal, synanthropic birds of prey remains poorly understood. This thesis investigated the effects of a short-term artificial light at night exposure on parental behavior and physiological responses in breeding Western barn owls (Tyto alba) in western Switzerland. Using a multi-method approach combining GPS tracking, camera traps, a perch-weighing system, and corticosterone measurements as an indicator of physiological stress, I found that light exposure delayed the first nocturnal visit to the brood and increased overall presence near the nest, particularly in the presence of moonlight. Individuals with redder plumage spent more time in proximity to the nest box compared to whiter conspecifics. Corticosterone concentrations were elevated following light exposure, especially in whiter individuals. Additionally, males exposed to light showed a decrease in body mass, with the most pronounced reduction observed in reddish individuals. These findings provide experimental evidence that even short-term exposure to artificial light at night can alter both behavioral and physiological traits in a nocturnal predator, highlighting the need for future research and conservation strategies to reduce the ecological impacts of light pollution in human-dominated landscapes.