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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Although most concern around the impacts of light pollution on breeding seabirds centres on lights on land, vessels at sea can also affect large numbers of seabirds that visit their colonies at night. In the 1980s, vessels fishing for rock lobsters around Tristan da Cunha killed hundreds of petrels each year when they were attracted to the ships' lights at night. Subsequent measures to reduce deck lighting to a minimum, and to cover all windows and portholes at night, have greatly reduced mortality in this fishery, but small numbers of petrels are still killed each year. Over the last eight years, petrels have been reported coming aboard fishing vessels on 13% of nights. These ‘night strikes’ are more common at the start of the breeding season in early summer and especially in autumn, when most petrel chicks leave the breeding islands. Night strikes can also occur at sea in the Southern Ocean well away from breeding islands. We recommend that all vessels operating in these waters should be required to black out all but the most essential lights, especially on dark nights, and when operating close to breeding islands. More info at: Ryan PG, Ryan EM, Glass JM, 2021. Dazzled by the light: the impact of light pollution from ships on seabirds at Tristan da Cunha. Ostrich
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October 2023
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