New York: Artificial lights in the cities are luring migrating birds, threatening them with death, a new study has revealed. Nearly 1,000 birds were killed in October when they collided with an illuminated glass building in Chicago. Though mass fatalities of this magnitude are rare, light pollution poses a serious – and growing – threat to migrating birds, according to the study published in the journal Nature Communications. Scientists used weather radar data to map bird stopover density in the US and found that artificial light is a top indicator of where birds will land. “City lights lure birds into what can be an ecological trap,” said lead author Kyle Horton, assistant professor in Colorado State University. Buildings that lead to collisions, less habitat, scarcer food, and more people and cats can make cities less-than-ideal rest stops for migrating birds. "These stopover locations are the fueling stations. If you're on a cross-country trip and there's no fueling stations, then you're stranded. If they don't have a good spot to rebuild energy supplies, migration can't happen,” said Horton. The study provides the first continent-wide maps of migration stopover hotspots in the contiguous US, and knowing these broad-scale layover patterns can help in the development of conservation plans. Also ReadNew online threat: How to protest yourself from digital arrest “Cities pose multiple risks to migrating birds. They also offer resources for the tired birds to rest and refuel. Our study is notable in that it combines big data – and a lot of processing – from the weather surveillance radar network with big data from multiple spaceborne sensors to address key questions regarding the influence of urban areas on bird migration,” explained co-author and Michigan State University Professor Geoff Henebry. There can be social pressure to leave lights on, and some people find them aesthetically pleasing. But light pollution harms people too. It can disrupt humans’ circadian rhythms, leading to health problems including depression, insomnia, cardiovascular disease and cancer. "We don't often think about light as a pollutant, but it checks all the boxes of what pollution is,” Horton said. Public awareness of bird migration habits would be a good place to start to help protect them from light pollution.