Migratory songbirds face a gauntlet of human-caused hazards including window strikes, cat predation, and light pollution that kill billions of birds annually in North America alone.
Window strikes cause acute traumatic injury - internal hemorrhage, brain injury, and spinal trauma from collision with glass that birds cannot perceive as a barrier. Many birds die immediately while others are stunned and die from cold or predation while incapacitated. Cat predation causes trauma and terror with many birds surviving initial capture only to die from infection or shock. Light pollution exhaustion occurs when migrating birds are drawn to illuminated buildings, circle disoriented for hours burning critical energy reserves, then die from exhaustion or strike the building. These billions of individual mortality events represent enormous aggregate suffering concentrated in a few weeks of migration periods each year - and most are preventable through simple household changes.