Take Home Message: Light pollution kills millions of migratory birds each year by causing them to collide with windows. Toronto and Chicago pioneered Lights Out programs to limit light pollution during times of heavy bird migration, and cities across America have followed suit. You can help prevent bird-window collisions by turing off lights at night during the spring and fall, bird-proofing your windows, keeping domestic cats indoors, and volunteering with your local Audubon society.