Migrating birds set to risk their lives flying over Chicago, most dangerous city for migratory birds in North America

Migratory bird movement is in full swing, and experts are urging Chicagoans to turn off their lights at night to help protect the birds over the next few days from fatal window collisions.

Thousands of birds carpeted the sky last night, according to Annette Prince, director and president of Chicago Bird Collision Monitors, a nonprofit dedicated to the respite and protection of migratory birds through daily rescue efforts, when on Thursday Chicago experienced a drastic shift in wind patterns moving up from the south, prompting waves of birds to pass through downtown looking for green space to settle.

Chicago is located on the Mississippi flyway, and birds pass through the city on their journey north toward Canada in search of a good place to nest and breed for the summer.

On her way to work this morning, Prince found a little bird in the street, stunned.

"He couldn't even move, he just sat there blinking and hurt," she said. "It would have been just a matter of seconds before a car came and ran him over."

Birds fly at night to protect themselves from predators. They navigate using the moon and stars, but artificial light from city buildings can skew their flight and make them crash into glass.

This morning, the CBCM hotline was swamped with calls from people around the city. Prince said after a night like Thursday, it's not uncommon for people to look out onto rooftops from their downtown offices and find them littered with dead and dying birds.

During key migration months—spring and fall—CBCM leads volunteer groups ranging between eight and 20 people to walk around skyscrapers and scoop up fallen flyers. They take the injured ones to the Willowbrook Wildlife Center in Glen Ellyn for rehabilitation and care, and take thousands of dead birds each year to the Field Museum, where they are added to the collection for documentation and research.

Using weather surveillance radar techniques, real-time bird migration numbers can be found online at BirdCast. Researchers from the Field Museum are now also going out across Illinois to conduct a spring species count from the ground.

CBCM volunteer groups collect up to 7,000 birds each year, about a quarter of which are injured, said Prince.

"And that's just the tip of the iceberg. That's just what we've found, and what people report to us," she said.

A study published in June found that bird collision mortality could be reduced by about 60% if artificial light was cut in half. This would have global implications, as birds are a critical part of controlling insects, distributing seeds, and pollinating plants.

"These birds are doing a really hazardous thing, and we make it even more hazardous by putting buildings along the lakefront," said John Bates, curator of the division of birds at the Field Museum.

Chicago has been ranked as the most dangerous city for migratory birds in North America by the Cornell Lab of Ornithology.

In July 2021, Gov. J.B. Pritzker signed the Bird Safe Buildings Act, requiring bird-safety building features to be implemented in construction and renovation of state-owned buildings in Illinois.

But Prince said she has heard bird strikes are increasing in the West Loop, as skyscrapers, stores and restaurants bring more glass to downtown Chicago. Thrushes, orioles, woodpeckers, yellow-bellied sapsuckers and herons are among the species of birds she and her volunteers pick up on any given morning.

"The glass confuses them—because it's clear and they think they can fly into it, or they think it's a tree and it's really the reflection of a tree," said Prince.

Prince said sometimes she finds birds that weigh as little as two pennies. They're spectacular, she said. Bright orange, yellow and red.

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