Window collisions kill an estimated one billion birds annually in North America alone, making glass buildings a major and largely preventable source of bird mortality and suffering.
Birds that survive window strikes often sustain serious injuries including concussion, brain hemorrhage, and broken bones. Even birds that appear to recover and fly away may die hours later from internal injuries. The suffering of individual birds struck by windows is real and the scale across North America is enormous. Prevention is simple and inexpensive — applying visual markers to glass at close intervals prevents birds from perceiving the glass as open space. This is among the most accessible and high-impact wildlife welfare actions available to individuals.