Window strikes kill an estimated 600 million birds annually in the US alone. Understanding why birds collide with glass and how to prevent it can significantly reduce this preventable source of suffering.
Window strikes represent an enormous source of bird welfare harm that originates within domestic and commercial buildings — making every building owner a potential welfare actor. Birds that die on impact experience an abrupt, traumatic death. Many apparent survivors — birds found stunned at the base of windows — die within hours or days from internal haemorrhage, organ damage, or concussion injuries that are invisible externally. The welfare intervention opportunities are clear and proven: visual markers on glass surfaces that break up the reflection at 5cm or less spacing, exterior netting or screens, and the elimination of interior light visible through windows at night. These solutions range from low-cost temporary films to permanent bird-safe architectural glass. The scale of the problem — hundreds of millions of individual deaths annually — makes even modest adoption of preventive measures a meaningful welfare contribution.