Window strikes kill an estimated 600 million birds annually in the United States alone. Simple, evidence-based window modifications can prevent the majority of these deaths and injuries.
Window strikes represent a welfare harm that is both enormous in scale and highly preventable. The collision event itself causes acute trauma: birds hitting glass at speed suffer blunt force injury to skull, brain, and internal organs. Birds found alive after strikes — stunned, sitting motionless under a window — are experiencing the aftermath of traumatic brain injury, and many die hours later even when apparently recovering. The suffering involved in dying from internal hemorrhage or brain injury over hours is significant. What makes this welfare problem unusual is that effective solutions exist, are inexpensive, and can be applied by individuals to their own windows without systemic change. External window treatments — patterned films, screens, netting, and external blinds — break the reflective or transparent appearance of glass and prevent strikes. The spacing rule for external treatments is well-established: horizontal elements spaced no more than 10 cm apart or vertical elements no more than 5 cm apart effectively deter birds.