Window collisions kill hundreds of millions of birds annually. Simple, cost-effective prevention measures can dramatically reduce this welfare harm in homes, offices, and public buildings.
Window collisions represent one of the largest sources of direct human-caused bird mortality, yet they are almost entirely preventable. Birds that strike windows at speed suffer traumatic brain injury and skeletal fractures. Many die immediately; others stagger away and die later from internal injury or predation while incapacitated. The physics of the problem is well understood: birds cannot perceive glass as a solid barrier, particularly when windows reflect vegetation or sky. Solutions range from affordable DIY decals and tape strips to commercial UV-reflective films that are effective without significantly reducing human light transmission. Commercial architecture — with its vast glass facades — is a particularly high-collision-risk context, and requiring bird-safe glazing in new buildings would reduce mortality at scale.