Light pollution Light is one of the more common threats to sufficient sleep for birds living in environments with anthropogenic noise. This threat is called "artificial light pollution at night" , or ALAN. ALAN takes a substantial toll on avian sleep since it eliminates darkness, a key component for rest. Disrupting the birds' natural observance of light and dark cycles can disrupt circadian rhythmsand eventually harm vital sleeping patterns. For example, biologist Thomas Raap conducted a study that suggested exposure to ALAN affected the sleep behavior of great blue tits (Cyanistes caeruleus).Raap, T.; Sun, J.; Pinxten, R. & Eens, M. (2017). "Disruptive effects of light pollution on sleep in free-living birds: Season and/or light intensity-dependent?". Behavioural Processes: 144. In this study, birds woke up earlier due to various ALAN factors , such as seasonal time keeping . Because light usually indicates a day's passing to birds, exposure to light pollution caused a disruption in the birds' ability to measure the length of a full day. Outside of densely populated areas there is normally around a 5\% drop in sleep duration for Great Tits' females during their nesting period. However, the researchers found a 50\% reduction in the female Great Tits' total sleep duration during this period in densely populated urban centers. The researchers suggested that the direct effects of ALAN were to blame for this sleep disruption .
Light pollution Light is one of the more common threats to sufficient sleep for birds living in anthropogenic environments, known as "artificial light pollution at night" (ALAN). ALAN eliminates darkness, a necessity for rest. Disrupting the birds' light and dark cycles can impact circadian rhythms, eventually harming sleep patterns. Biologist Thomas Raap conducted a study which suggested that exposure to ALAN affected the sleep behavior of Eurasian blue tits (Cyanistes caeruleus).Raap, T.; Sun, J.; Pinxten, R. & Eens, M. (2017). "Disruptive effects of light pollution on sleep in free-living birds: Season and/or light intensity-dependent?". Behavioural Processes: 144. In this study, birds woke up earlier due to ALAN factors such as seasonal timekeeping . Because light usually indicates a day's passage to birds, exposure to light pollution disrupts their ability to measure the length of a day. Outside densely-populated areas, there is normally about a five-percent drop in sleep duration for blue-tit females during their nesting period. The researchers found a 50-percent reduction in the females' sleep duration during this period in urban centers, and suggested that the effects of ALAN were responsible .
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