Like other Procellariiformes, fledgling Manx shearwaters are affected by light pollution during their first flights. They come to the light, are somehow confused, and they land on the ground. While much research has been focused on understanding this phenomenon, only a few papers have been dedicated to explore how shearwaters are affected by light at a later stage of life. This study used a thermal imaging camera to record flying Manx shearwaters in a dense breeding colony. We used a small torch covered with different colours and intensity-blocking filters to investigate the effect of light on adult seabirds. Once all the videos were recorded, we used supervised machine learning to count the number of birds in different treatments. The results showed that adult Manx shearwaters avoided light stimulus at heir colony, and this avoidance depended on the light intensity, colour and duration. We counted less birds when we turned on strong intensity white light compared to the dimmed white. A similar intensity of blue, green and white light resulted in a similar avoidance in Manx shearwaters. But when we turned on a red light of similar intensity, we did not see any effect, suggesting that birds did not avoid our red light. Finally, longer duration of light-on interval results in a lower number of counted birds. These results suggest that turning on the light at a colony of shearwaters should be limited to a minimum. If the light is necessary, a low intensity and short duration of light, as well as light with more red components, should be preferred. Lastly, further research that investigates animals that might avoid light should be undertaken, since it is a phenomenon that is much harder to detect than attraction where animals congregate near light. More info at: Syposz et al. 2021. Avoidance of different durations, colours and intensities of artificial light by adult Manx shearwaters. Scientific Reports.
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