Billions of birds die annually from collisions with human structures. Simple mitigations at buildings, roads, and energy infrastructure reduce this massive source of wild bird welfare harm.
Bird window collisions represent a massive, diffuse, largely invisible welfare problem. A bird that strikes a window at speed experiences a traumatic impact causing concussion, internal haemorrhage, fractures, and eye injuries — often death. The welfare cost is acute and the suffering real, even for birds that recover sufficiently to fly away, as internal injuries may cause delayed death. The scale is extraordinary — hundreds of millions of events annually in North America alone. The good news is that effective mitigations exist: external window treatments with vertical elements spaced no more than 5cm apart effectively communicate to birds that the surface is a barrier; UV-reflective patterns visible to birds' tetrachromatic vision work without disrupting human window aesthetics. These solutions require awareness and modest cost rather than technological breakthrough. Building design codes that require bird-safe glass in new construction, combined with retrofits on existing high-collision buildings, represent the most scalable welfare intervention.