13-05-2025
It's peak spring migration season in Chicago, and residents can help birds arrive safely by turning their lights off at night
CHICAGO (WGN) — As the weather warms and summertime approaches in Chicagoland, you'll hear the chirping of more and more birds.
That's because millions are coming to the area during the peak spring migration season. And to help them arrive safely, area residents can turn their lights off at night.
According to BirdCast's migration dashboard, most birds pass through the contiguous U.S. from mid-April to mid-May. For our area, the peak migration time is right now.
An estimated 2,270,400 birds passed into Cook County overnight Monday into Tuesday, according to BirdCast. The peak was reached around 2:30 a.m. Tuesday, when an estimated 425,100 birds crossed into Cook County, flying at an altitude of 2,200 feet and a speed of 30 miles per hour.
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BirdCast says nearly 31 million birds have been estimated to have migrated into Cook County from March 1 through the overnight hours of Monday into Tuesday. The highest nightly traffic thus far was recorded on Friday, May 9, when an estimated 346,900 birds were in flight, on average, at one time.
These high traffic totals will keep Chicago on 'high migration alert' this week. You can check HERE on BirdCast for alert details.
Birds usually begin to migrate 30 to 45 minutes after sunset, according to BirdCast, with the greatest number in flight two to three hours later.
So with such large numbers of birds migrating at night, area residents are asked to help protect them by turning off all non-essential lighting from 11 p.m. until 6 a.m. while the 'high migration alert' is in effect, which includes overnight Tuesday into Wednesday.
According to BirdCast, bright lights attract and disorient nocturnally migrating birds, potentially causing fatal collisions with buildings or exposure to additional day-time hazards.
In cities like Chicago, for example, the windows of high-rise buildings can pose great danger for migrating birds, a problem that's come into focus during the fall migration, when birds sweep south following the Lake Michigan shoreline.
About 1,000 migrating songbirds were killed over a single night on Oct. 4-5, 2023, after flying into the windows of McCormick Place. In response, McCormick Place installed bird-safe window film over its two football fields' worth of glass windows, which was in place in time for the 2024 fall migration season.
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According to BirdCast, these are the species most likely to arrive to Cook County during the spring and depart during the fall: American Redstart, Magnolia Warbler, Chestnut-sided Warbler, Baltimore Oriole, Wilson's Warbler, Indigo Bunting, Tennessee Warbler, Least Flycatcher, Swainson's Thrush, Eastern Wood-Pewee, Warbling Vireo, Scarlet Tanager, Blackburnian Warbler and Blackpoll Warbler.
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