Migratory songbirds face a gauntlet of human-created hazards during twice-yearly migrations that take enormous physiological tolls.
Migratory birds expend enormous energy reserves during migration with no margin for additional stressors. When they arrive at stopover sites stripped of food by early spring warming, or when they exhaust reserves over the ocean, they die from starvation and exhaustion. Window strikes cause acute trauma. Cats kill exhausted migrants that land to rest. Each human-created hazard along migration routes compounds the physiological toll of migration itself.