Chicago officials have issued a bird migration alert asking residents and building managers to turn off or dim unnecessary exterior lights between 11 p.m. and 6 a.m. over the next three nights, as nearly 300 million birds are expected to take flight across the United States. Cool, dry weather is encouraging birds to travel southward overnight, and Chicago and the Great Lakes sit along one of North America’s busiest flyways.
The alert, first reported by NBC Chicago, cites figures from Chicago Animal Care and Control estimating nearly 300 million birds will be aloft over the country in the coming days, part of a broader wave of more than 825 million birds expected to migrate across the nation in the days ahead. More than 150 million birds have already traversed Illinois this season alone, according to the same report, as flocks head toward their winter homes. Data behind the alert comes from BirdCast, a tracking project spearheaded by Cornell and other organizations that models migration volume using weather radar.
Bright lights can attract and disorient birds in flight, increasing the risk of collisions that injure or kill them, and officials are asking high-rise residents and workplace occupants to close blinds and curtains so birds can more clearly see their path through the city skyline and surrounding suburbs. Closing blinds also reduces light pollution more broadly. Residents and property owners are being asked not to illuminate lobbies, fountains, or plants that can attract birds toward glass.
Why Chicago Is Ground Zero for Collision Risk
The urgency behind these seasonal alerts is rooted in hard data: a 2019 study led by the Cornell Lab of Ornithology, published in Frontiers in Ecology and the Environment, ranked Chicago as the single most dangerous U.S. city for migratory birds in both spring and fall, largely due to its light pollution and position on the Mississippi Flyway, according to the Cornell Chronicle. Houston and Dallas ranked second and third. An estimated 5 million birds representing roughly 250 species pass through the Chicago urban corridor each year during their seasonal migrations, per BOMA Chicago…