Window Strikes: Reducing Bird-Building Collisions

Window strikes kill up to 1 billion birds annually in North America alone, making them one of the largest human-caused sources of bird mortality.

Key Facts

Windows are responsible for 100 million to 1 billion bird deaths annually in the US
Birds cannot perceive glass as a barrier, seeing reflections of sky and vegetation
Collisions cause acute trauma including broken necks, internal hemorrhage, and concussion
Strikes peak during migration when large numbers of birds move through urban areas
Simple deterrents including window film, screens, and external netting dramatically reduce strikes

Welfare Considerations

Birds that strike windows experience acute trauma ranging from fatal immediately to delayed death from internal injury. Many collisions cause concussion from which birds may appear to recover before dying hours later. The cognitive inability to perceive glass as a barrier means that without human intervention, individual birds repeatedly strike the same window. The scale of the problem — potentially a billion deaths annually in North America — makes window strike reduction one of the most tractable welfare interventions available to individual householders.

What You Can Do

Apply window treatments including films, dots, or external screens on windows where strikes occur
Place bird feeders either very close to or more than 3 meters from windows to reduce strike risk
Check for stunned birds after hearing strikes and provide supportive care if found
Advocate for bird-friendly building standards in new construction codes