For one week this fall, Darci Gabriel spent the first hour of her day scanning the sidewalks of downtown Minneapolis’ Mill District for small brown lumps lying still among the fallen leaves. They’re bird carcasses, the result of window collisions as migratory birds travel through the Mississippi Flyway en route to their winter destinations.
In the northwest side of the Bridgewater Lofts condominium, Gabriel finds one dainty gray bird with a lime-yellow throat, lying prone with its feet tucked up. She snaps a photo, then logs its location and her best guess at its species — Tennessee warbler — in a Survey123 mobile app that bird lovers use worldwide to track bird vs. building collisions and inform scientific research on bird mortality. Then she scoops the carcass into a Chinese takeout container to donate to the Wildlife Rehabilitation Center in Roseville.
She rounds the corner of Bridgewater Lofts and immediately finds another one.
“Hopefully something can be done, even if it’s just having people dimming their lights in the evenings,” said Gabriel. “Just having downtown dimmed down would actually help prevent a lot of the migratory birds coming into the city to begin with.”
The Mill District, where Gabriel lives, has undergone heavy development in the last 20 years, with high-rise condos displacing warehouses and surface parking lots from their prime locations along the Mississippi River. The area is also a migration route, with birds hardwired to follow the open river north and south each spring and fall to avoid mountains and other towering obstacles.
With the built environment of our urban centers rapidly outpacing the evolution of migratory birds, strikes happen because birds don’t register glass as solid and impenetrable. When the sun rises and downtown skyscrapers reflect the foliage of the boulevard trees, birds careen into buildings when they think they’re aiming for the leafy landscaping, scientists believe.

Collision hot spots
The Audubon Chapter of Minneapolis collected strike data during both spring and fall migrations this year, focusing on hot spots including the U.S. Bank Stadium, residences along the river and downtown skyways. A handful of volunteers working about an hour each morning for a week took in 54 birds, including 43 dead on arrival, three that died from their injuries, three in care and five released after rehab.
“Our approach with building owners and managers is to raise awareness about the magnitude of the effect of window collisions on total bird populations, the impact their building is having and solutions to mitigate that impact,” said Jeannine Thiele, vice president of the local Audubon, which advocates for the use of bird-safe glass in new construction and cities’ participation in the Lights Out program.