Effects of artificial light with different wavelengths and irradiances on the sleep behaviors of Chestnut buntings (<i>Emberiza rutila</i>)

Abstract

Artificial light owns a rapid-expanding pattern, which may disrupt the sleep behaviors of birds roosting in illuminated urban areas. Whether the birds’ sleep would variably be affected by light with different wavelengths or intensities has not been broadly explored, and the species in Eastern China have rarely been investigated. The study chose Chestnut buntings that are a common migratory species flying via Eastern China as the subjects and investigated their sleep in response to five light spectrums at three ecologically relevant intensities. It shows that artificial light mainly delayed sleep onset, reduced sleep duration and increased frequency of awakenings, which to the largest degrees resulted in a 3-h delay of sleep onset, 25% reduction of sleep and 0.31 times/h more nocturnal awakenings. Awakening time was delayed at higher light intensity while being advanced in dimmed light. The effect of light spectrums overall ranked from the most to the least as 510 nm green, 580 nm yellow or white, and 470 nm blue or 620 nm orange light; the sleep parameters were affected more with higher light intensities. The study highlights the potential of adjusting spectral compositions of light source to mitigate the disturbance of artificial light to avian sleep.