Window Strike Prevention: Saving Billions of Birds

Window collisions kill an estimated 600 million to 1 billion birds annually in the United States alone, making buildings one of the most significant anthropogenic causes of bird mortality - yet most window strikes are preventable.

Key Facts

Birds see reflected sky and vegetation in glass and cannot perceive the transparent barrier
Up to 1 billion birds die from window strikes in the US annually - second only to cat predation
Most window strikes occur at residential properties, not skyscrapers - ordinary homes are responsible for the majority
Vertical stripes or dots spaced no more than 5cm apart on windows effectively break up reflections
Acopian BirdSavers (paracord strings) are highly effective and aesthetically acceptable for many homeowners
Dawn and dusk are peak collision times when birds are most active
Migration periods in spring and autumn see elevated collision rates as birds move through unfamiliar areas
Treated birds that survive initial impact often have internal injuries and require wildlife rehabilitator care

Welfare Considerations

Birds that collide with windows experience acute trauma - brain injury, internal hemorrhage, and broken bones are common outcomes. Many birds that appear to recover and fly away die hours later from internal injuries. The annual toll of hundreds of millions of birds represents an enormous sum of individual suffering that most building occupants are entirely unaware of. Prevention is straightforward and inexpensive - a few dollars of window markers or bird-safe film eliminates the vast majority of collisions from treated windows. This is one of the highest welfare-impact-per-cost interventions available to individual households.

What You Can Do

Apply bird-safe window markers, film, or Acopian BirdSavers to windows where strikes occur
Move bird feeders to within 30cm of windows (too close for lethal impact) or more than 10m away
Turn off unnecessary indoor lights during peak migration periods (spring and autumn nights)
If you find a stunned bird, place it in a dark box and contact a wildlife rehabilitator
Advocate for bird-safe building standards in new construction and major renovations