In the largest study of its kind, scientists used weather radar data to map bird stopover density in the United States 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 – with buildings that lead to collisions, less habitat, scarcer food, and more people and cats. The study, led by Colorado State University, provides the first continent-wide maps of migration stopover hotspots in the contiguous United States, and knowing these broadscale layover patterns can help in the development of conservation plans.