In 2018, a student at Duke Kunshan University in China’s Jiangsu Province, saw a tiny warbler with green feathers majestically flying toward the glass window of her school building.
But instead of maneuvering, the bird hit the glass, making a gentle thumping sound and leaving behind a tiny mark on the window.
Shocked by the bird’s poor navigation capabilities, she later learned the warbler’s dead body hurtled to the ground and was cleared off by the staff on duty. The bird-hit stain on the glass and the feeble noise of collision symbolizes the unnoticed deaths that buildings in cities have caused.
Every year 100 million to one billion birds die from collisions with buildings in the U.S. alone, according to the U.S. Fish & Wildlife Service. Residential buildings fewer than four-stories also contribute to such fatalities.
As carcasses of birds are immediately swept away by sanitation crews or devoured by predators, most incidents go unseen and unreported.