Billions of wild birds die each year from human-made hazards in urban environments. Window collisions, outdoor cats, and artificial light are among the most lethal threats.
Birds that strike windows often die immediately, but many suffer internal injuries and die slowly over hours. Cats that catch birds rarely kill instantly — prolonged predation causes significant suffering. Light-disoriented migratory birds may circle lit buildings for hours before exhaustion or collision kills them. Urban birds face chronic noise stress that elevates cortisol, disrupts communication, and impairs reproductive success. Even birds that survive urban hazards experience higher baseline stress levels than rural counterparts. These welfare harms occur at enormous scale but are largely invisible because they happen at night or in locations not easily monitored.