Light pollution, or artificial light at night (ALAN), is a widespread phenomenon in areas with dense human populations. Normally, animals use natural external cues, like sunlight and temperature, to synchronize their biological rhythms with the day-night cycle. However, ALAN is known to affect the biological rhythms of animals living within its range by altering physiological, molecular and behavioral mechanisms related to sleep-wake cycles (circadian rhythms).
Light pollution has more dramatic effect on circadian rhythms of social birds than isolated birds, study finds
