Window collisions kill an estimated 600 million to 1 billion birds annually in North America alone, making this one of the most significant human-caused bird welfare harms that can be substantially reduced.
Window strike welfare is a vast, largely preventable source of acute suffering and death. Birds striking glass at full flight speed may die instantly or survive with concussion, internal hemorrhage, and disorientation that leaves them vulnerable to predation. The preventable nature of this mortality — through widely available window treatment products — makes every untreated window contributing to bird collisions a welfare failure that informed action can address. Individual homeowner action on window treatments, combined with building design standards requiring bird-safe glass, could prevent hundreds of millions of bird deaths annually at relatively low cost.