Collisions with buildings kill an estimated 600 million birds in the U.S. every year, according to the Cornell Lab of Ornithology.
The top three most dangerous cities for bird collisions—Chicago, Houston, and Dallas—are located within the heart of North America’s most trafficked aerial corridors, according a new Cornell study.
That fact, along with their considerable size, makes these cities dangerous to migrating birds in the spring and fall.
Seventy percent of bird species in the U.S. are migratory, and more than 80% of those migrate at night. Urban light pollution attracts avian travelers, leading them to crash into buildings.
Strategies to prevent these usually fatal collisions include constructing bird-friendly buildings with patterned glass or dimmer lights. Lawmakers in New York and Chicago are considering legislation to improve bird safety into new building rules.