Window collisions kill an estimated 300 million to 1 billion birds annually in North America alone, making building glass one of the most significant sources of direct human-caused bird mortality.
Window strikes cause blunt trauma injury ranging from temporary concussion to immediate fatal impact. Birds that survive initial impact may die later from internal bleeding or neurological damage. The scale of mortality — potentially billions of birds annually globally — makes this one of the largest preventable sources of direct human-caused bird suffering. Individual action at home is unusually impactful because most strikes occur at private residences rather than commercial buildings. Applying window deterrents to even one collision-prone window can prevent dozens of bird deaths per year.