Lost in the Light: Effects of Exposure to Artificial Light at Night on Migratory Birds

Artificial light at night (LAN) is expanding globally, changing the natural landscape and imposing novel ecological pressures on wildlife. Birds, like most organisms, use natural light information to regulate their daily and seasonal behaviors, including the precise timing for migration and reproduction. The presence of LAN has, however, blurred the day-night boundaries thereby leading to misinterpretation and physiological and behavioral desynchronization. This review synthesizes current knowledge of how LAN affects migratory birds, with a focus on their orientation and navigation, attraction to urban centers, increased risks of collisions, altered nocturnal predator-prey dynamics, disrupted foraging behavior, and interference with hormonal rhythms that are critical for migratory preparedness. In addition to highlighting these direct and indirect ecological consequences, we critically examined the existing mitigation strategies aimed at reducing the impact of LAN. With this, we have identified that while a few research focus on understanding LAN effects and its mitigation methods, there is a significant knowledge gap in understanding its mechanistic pathways and long-term fitness consequences for migratory birds. Furthermore, the body of applied knowledge available to mitigate LAN effects is still very limited. We conclude by identifying and discussing several key areas for future work.