More than 1,000 migratory birds were killed or injured after colliding with buildings in Chicago and Evanston on October 17 and 18, 2026, according to Chicago Bird Collision Monitors. The mass collision has renewed calls for a bird-friendly building ordinance that has been waiting in the City Council’s Zoning Committee since July.
Key Takeaways
- Volunteers collected the birds in downtown Chicago and on Northwestern University’s Evanston campus over the October 17–18 weekend.
- BirdCast estimated that about a billion birds were in flight over the contiguous United States on the night of October 17.
- The proposed ordinance would set bird-safe glass and lighting standards for new construction and major renovations in Chicago.
- After 960 birds died at McCormick Place Lakeside Center in a single night in October 2023, markers added to its glass cut collisions by 95%, according to Bird Friendly Chicago.
- Chicago Bird Collision Monitors typically recovers 5,000 to 6,000 birds a year within a 1.5-square-mile downtown zone.
Why Do Birds Fly Into Windows In Chicago
Chicago sits along one of North America’s major migratory routes, and the city’s glass skyline lies directly in the path. “Major events like this occur because Chicago is a major migratory path for millions of birds,” said Annette Prince, director of Chicago Bird Collision Monitors.
Two factors drive most collisions. Reflective glass can look like open sky or trees to a bird, which gives it no signal that a solid surface is there. Artificial light at night compounds the problem by drawing nocturnal migrants toward buildings. Research at McCormick Place found that shutting off even half of the building’s lights reduced bird collisions by six to 11 times.
The weekend of October 17 combined both factors with unusually heavy migration. BirdCast, the migration forecasting project, estimated that about a billion birds were in flight over the contiguous United States that Friday night. Chicago Bird Collision Monitors volunteers, who routinely search downtown before sunrise during spring and fall migration, said the weekend’s numbers were especially high.
Bird Migration Chicago Volunteers Track Collisions Year-Round
Chicago Bird Collision Monitors is a volunteer-led conservation group that rescues injured birds and documents those that die after striking buildings. Over the October 17–18 weekend, volunteers searched downtown Chicago and Northwestern University’s Evanston campus, collecting dead birds and rescuing injured ones.
The weekend stood out against the group’s regular numbers. Chicago Bird Collision Monitors typically recovers between 5,000 and 6,000 injured or dead birds a year within a 1.5-square-mile downtown zone. More than 1,000 in a single weekend represents a large share of that annual total arriving in two days.
Chicago has seen events like this before. In early October 2023, 960 birds died at McCormick Place Lakeside Center in a single night. Experts described it as the highest number of bird-collision deaths recorded in the United States in one day.
Bird Safe Glass Ordinance Moves Slowly Through City Council
The policy response has been years in the making. In 2020, rather than pass a bird-friendly building law, the City Council directed the Department of Planning and Development to give greater weight to bird-friendly design within the city’s Sustainable Development Policy. That approach rewards developers for including bird-safe features but does not require them.
A new ordinance was introduced in 2026, the second attempt since 2019. At the March 18 City Council meeting, Ald. Anthony Beale (9th) sent it to the Rules Committee. In July, supporters freed the measure from Rules, and it was sent to the Zoning Committee, where it remains. The proposal would establish bird-safe glass and lighting standards for new construction and major renovations. Its lead sponsor, Ald. Maria Hadden (49th), chairs the Committee on Environmental Protection and Energy.
Advocates point to other cities as models. New York, San Francisco, and Toronto have all passed bird-friendly building laws. “Chicago must require that future buildings use bird-friendly building designs and materials so we do not add to the devastating toll existing structures take on bird life,” Prince said after the October weekend.
The building industry has raised cost concerns. At a 2025 City Council hearing, opponents argued that an ordinance would add regulation and expense to new construction. The Building Owners and Managers Association of Chicago said owners would struggle to absorb the cost of any requirement to retrofit existing glass. The current proposal focuses on new construction and major renovations rather than requiring retrofits across existing buildings.
McCormick Place Shows What Bird-Safe Design Can Do
The clearest local evidence comes from McCormick Place. After the 2023 collision event, visible markers were added to the Lakeside Center’s glass. Bird collisions at the building later dropped by 95%, according to Bird Friendly Chicago.
Chicago also relies on a voluntary approach. Lights Out Chicago, which has run since 2000, encourages building managers to turn off decorative upper-story lights after 11 p.m. during migration. Bird Friendly Chicago is urging continued support for the program alongside the ordinance, arguing that voluntary dimming and mandatory glass standards address different parts of the same problem.
FAQs
Why Do Birds Fly Into Windows?
Birds often cannot see glass. Reflective windows can mirror the sky or trees, and lights at night draw migrating birds toward buildings, which raises the risk of collisions during spring and fall migration.
What Is Bird Safe Glass?
Bird-safe glass uses patterns, markers, or other treatments that make windows visible to birds. Chicago’s proposed ordinance would set bird-safe glass standards for new construction and major renovations.
How Do You Prevent Birds From Hitting Windows?
Common approaches include visible markers or patterned glass, exterior screens, and reducing nighttime lighting. At McCormick Place, adding visible markers to the glass cut bird collisions by 95%, according to Bird Friendly Chicago.
What Is Lights Out Chicago?
Lights Out Chicago is a voluntary program, running since 2000, that encourages building managers to turn off decorative upper-story lights after 11 p.m. during migration seasons to reduce bird collisions.
