As hundreds of millions of birds migrate northward for their spring breeding season, the city of Chicago has a critical role to play in keeping the animals safe.
Benjamin Van Doren, an assistant professor of environmental sciences at the University of Illinois at Urbana-Champaign, says that Chicago’s location in the Midwest and along the Great Lakes puts it right at the epicenter of the flight path of millions of birds.
“Chicago is a city that rests on a really important migratory flyway for migratory birds,” he said. “It’s right on the Great Lakes, and there are lots of birds passing through.”
Those bird species are continuing to pass through in breathtaking numbers in recent days, with 24.5 million birds flying in Illinois at approximately 11 p.m. Sunday night. More than seven million birds crossed out of the state as they make their way northward to breeding grounds in Wisconsin and Canada, with everything from Yellow Warblers to Baltimore Orioles passing through.
Van Doren wants to remind Chicagoans of the critical role the city plays in keeping birds safe, something that it has struggled to live up to.
“Chicago is the city that likely exposes the most migratory birds to the most light pollution of all U.S. cities,” he said.
Lights Out Chicago has been encouraging businesses to participate since the 1990s.
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Businesses and apartments are asked to extinguish or dim exterior lighting on multi-story buildings. Buildings are also asked to extinguish or dim the maximum amount of lobby lighting between 11 p.m. and 6 a.m.
Birds are most active around 11 p.m. at night, typically beginning their nightly flights 30-to-45 minutes after sunset.
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Even changes as subtle as rain in the forecast can lead birds to delay their flights, meaning that dry periods of weather like Chicago has seen on Sunday and Monday can lead to even more birds taking to the skies.
“Birds are actually very selective when they move in both the spring and the fall migration, so typically birds won’t decide to migrate if it’s facing a stiff headwind, or if it’s raining,” he said.
According to Birdcast, more than 320 million birds have already crossed over the state during the spring migration, which is above average for this time of year, something Van Doren says is occurring because of the effects of climate change.
“As the climate warms, as weather in the spring generally gets warmer, migrations are becoming earlier and earlier as birds try to adjust to the changing weather and climate,” Van Doren said.
Chicago is expected to see high volumes of migrating birds on both Monday and Tuesday nights, with residents urged to take steps to protect the animals.
You can find more information on the Lights Out Chicago program on the city’s website, and access to Birdcast maps through Colorado State University and the Cornell Lab of Ornithology.
