Walk around any city at dawn this time of year and you’ll likely encounter a grim, feathery graveyard. Migrating birds that have crashed into windows lie stunned or dead at the bases of buildings, only to be swept up by property managers or snatched away by predators as the sun rises.
Collisions with buildings and other human structures are perhaps the biggest contributor to avian fatalities in North America. Many species migrate by night and are perilously dazzled by artificial illumination, for reasons we don’t yet completely understand. Lights on skyscrapers, airports, and stadiums draw birds into urban areas, where they smack into walls and windows or each other, or flap around and eventually perish from exhaustion-related complications.