Bird Collisions Highlight Need for Bird-Friendly Building Design

Advocates and volunteers report that over 1,000 birds collided with buildings in the Chicago area during a recent fall migration weekend. Most of these incidents occurred in downtown Chicago and on Northwestern University’s Evanston campus, according to Chicago Bird Collision Monitors. Volunteers had anticipated a large number of migratory songbirds flying south on Friday night due to favorable north winds, intended to save energy as they journey hundreds of miles.

On Saturday alone, the DuPage Wildlife Conservation Center received 274 birds from downtown Chicago building collisions, with 60 more on Sunday. This involved over 20 bird species, including 80 golden-crowned kinglets and 73 brown creepers. Jennifer Bell, a volunteer with the collision monitors, observed birds falling every five seconds while checking sidewalks between sunrise and 1 p.m. She rescued 22 injured birds and found 40 dead.

Advocates argue this situation underscores the urgent need for effective preventive measures. They push for a Bird-Friendly Building Design Ordinance in Chicago to protect birds in new buildings. Besides policy actions, adjusting design choices and reducing light pollution in existing structures can reduce preventable collisions. Situated along the major migratory path known as the Mississippi Flyway, Chicago is especially hazardous for migrating birds.

Cornell University’s Lab of Ornithology’s BirdCast reported that over 5 million birds crossed Cook County on the night of the events. Annette Prince, director of the collision monitors, stressed the importance of maintaining safe passage for birds while preserving Chicago’s architecture. An estimated billion birds crash into windows in the U.S. annually. BirdCast notes approximately a billion birds were in flight over the contiguous states that Friday night.

“We are crucial to migratory routes evolved over tens of thousands of years,” Prince said.

Past events include an even more fatal mass collision in early October 2023 when 960 birds died at McCormick Place Lakeside Center. Experts described this as the largest recorded bird collision event in the U.S. Jennifer Bell mentioned that this year’s event felt similarly tragic.

This fall, Bell has rescued 350 birds, noting that collisions occur across the entire city, not solely in downtown or tall buildings. Annette Prince explained that birds often collide with glass up to 100 feet from the ground, creating accumulations like the recent event where 1,000 birds were affected. Observations and reports came from across the city, pointing to a widespread issue.

Glass structures pose significant risks to birds. Their reflective or transparent nature can deceive birds into collisions, often at high speeds resulting in fatal trauma. Nighttime artificial lights can also cause disorientation, increasing collision risks.

Allison Sloan, from Bird-Friendly Evanston, collected 42 injured birds over the weekend. Previous events have prompted advocacy for design measures like patterned glass, exterior screens, or other visible treatments that help birds identify windows as barriers. McCormick Place underwent changes after a deadly incident, applying a film with tiny dots, reducing collisions by 95% as analyzed by the Field Museum.

Doug Stotz, formerly with the Field Museum, emphasized the need for an ordinance requiring bird-friendly designs for new buildings. This ongoing problem led to suggestions for changes such as closing drapes and reducing non-essential light use. Chicago, alongside various organizations, promotes the Lights Out Chicago program since 1995, reducing nighttime lighting and saving many birds during migrations.

Prince expresses hope that city successes in reducing light pollution can extend through requiring bird-friendly features in new and renovated buildings. She emphasizes the urgency of acting on these measures to prevent future unprotected building projects, minimizing long-term negative impacts on migrating birds.

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