Glass windows and building facades are responsible for up to one billion bird deaths annually in North America alone, making collisions a major avian welfare issue.
Window collision causes instant death, concussion, or delayed death from internal injuries. Birds that survive the initial impact may be caught by predators while stunned, or die later from brain haemorrhage. The welfare impact is enormous in scale and largely preventable. Most collisions occur in residential settings, meaning individual household actions aggregate into significant population-level effects.