Light pollution from urban buildings during migration periods disorients billions of birds annually, causing fatal building collisions — a welfare and conservation crisis that is highly amenable to simple intervention.
Building strike welfare represents an enormous but largely invisible mortality source — most strikes occur in the dark and are cleared before daytime, making the scale difficult for the public to appreciate. Simple interventions including turning off interior lights in upper floors of tall buildings during spring and autumn migration periods can save tens of thousands of birds per building per migration season in high-risk locations. Urban building audits for bird strike risk and retrofit with bird-safe glass are achievable systemic interventions.