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Valentina Alaasam; Light at night disrupts nocturnal rest and elevates glucocorticoids at cool color temperatures. Journal of Vision 2019;19(8):116. doi: https://doi.org/10.1167/19.8.116.
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Nighttime light pollution is quickly becoming a pervasive, global concern. Since the invention and proliferation of light-emitting diodes (LED), it has become common for consumers to select from a range of color temperatures of light with varying spectra. Yet, the biological impacts of these different spectra on organisms with unique photoreception pathways remain unclear. We tested if nighttime illumination of LEDs, at two commercially available color temperatures (3000K and 5000K) and at ecologically relevant illumination levels affected body condition, food intake, locomotor activity and glucocorticoid levels in zebra finches (Taeniopygia guttata). We found that individuals exposed to 5000K light had higher rates of nighttime activity (peaking after one week of treatment) compared to 3000K light and controls (no nighttime light). Birds in the 5000K treatment group also had increased corticosterone levels from pre-treatment levels compared to 3000K and control groups but no changes in body condition or food intake. Individuals that were active during the night did not consequently decrease daytime activity. This study adds to the growing evidence that the spectrum of artificial light at night is important, and we advocate the use of nighttime lighting with warmer color temperatures of 3000K instead of 5000K to decrease energetic costs for avian taxa. We plan to follow this work by examining LAN-induced alterations to the circadian clock and by mapping immediate early gene expression in the avian brain, to better understand the mechanisms behind downstream behavioral and physiological effects.
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