Urban Wildlife

Night Flights and Bird Window Strike Mortality

Migratory birds are killed by window strikes in enormous numbers during nocturnal migration, especially during poor weather.

Key Facts

Window strikes kill an estimated 600 million birds annually in the US alone
Migratory birds flying at night are attracted to lit buildings and become disoriented by artificial light
Bird mortality is highest during spring and fall migration when billions of birds move through urban corridors
Tilted glass that reflects sky rather than vegetation reduces strike rates by over 90%
Lights Out programs during peak migration periods reduce bird mortality at participating buildings

Welfare Considerations

Window strikes cause death by traumatic brain injury, spinal injury, or immediate impact trauma. Birds that are stunned but survive the initial strike often die later from internal injuries. The scale of window strike mortality makes it one of the largest single human-caused sources of bird mortality, second only to cats.

What You Can Do

Apply bird-safe window film or collision tape to exterior windows, especially large reflective panels
Participate in or advocate for Lights Out programs in your city during migration seasons
Report window-strike deaths to monitoring programs such as FLAP Canada and American Bird Conservancy