David Willard, who has monitored bird fatalities at a Chicago exhibition center for 40 years, discovered hundreds of dead songbirds, clustered like a carpet. Avian experts attributed this tragedy to a lethal combination of migration conditions, rain, and the hall's lighting and windowed structure.
Willard, a retired museum manager, conducted migration research and tracked bird strikes as part of his duties at the Chicago Field Museum, which houses a vast collection of bird specimens. This incident underscores the ongoing issue of bird-window collisions, with hundreds of millions of birds dying in such strikes in the U.S. annually.
Millions of Birds Die of Window Strikes Every Year
Researchers estimate that window strikes claim the lives of hundreds of millions of birds annually in the United States. A 2014 study by the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service placed the number between 365 million and 988 million birds per year.
Bird-window collisions are a widespread problem in major U.S. cities. Birds often cannot differentiate between clear or reflective glass and open space, causing them to collide with windows. This issue occurs when birds see plants or greenery through windows or in reflections and mistakenly fly toward them, resulting in fatal outcomes.
Nocturnal migratory birds like sparrows and warblers, which rely on starlight for navigation, face particular challenges. Bright building lights can both attract and disorient them, leading to collisions with windows or, in some cases, birds continuously circling lights until they succumb to exhaustion-a phenomenon termed fatal light attraction. In an instance from 2017, nearly 400 passerines were disoriented by the floodlights of a Galveston, Texas skyscraper and died in collisions with windows.
Combination of Migration Season, Bad Weather, and Man-Made Lights
The event at McCormick Place in Chicago unfolded during a significant wave of southern migration for songbirds. These birds, which typically feed during the day and migrate at night to avoid turbulence and predators, had been delayed due to unusually warm southern winds in September. However, a southbound front with a tailwind on Wednesday evening led to thousands of birds taking flight over Chicago.
Unfortunately, they flew into a web of illuminated structures, resulting in numerous collisions. Pre-dawn rain forced the birds to descend to lower altitudes, where they encountered the lights at McCormick Place, leading to the tragic deaths of approximately 964 birds from 33 species, predominantly palm and yellow-rumped warblers.
Furthermore, the birds likely descended to lower altitudes due to pre-dawn rain, becoming attracted to the illuminated lights along the shoreline they were following. These artificial lights both lure and disorient nighttime migratory birds like sparrows and warblers, which typically rely on stars for navigation.
If they don't collide directly with buildings, they often circle the lights until exhaustion leads to their demise, a phenomenon known as fatal light attraction.
Experts point out that McCormick Place has a well-documented history of bird strikes, and Chicago was identified by Cornell University in 2019 as one of the most perilous cities for migrating birds. Before this incident, the highest collision numbers observed at McCormick Place were approximately 200.
Installing screens, using window paint or decals, and practicing nighttime light conservation can substantially lessen these yearly calamities, providing safeguards for migratory birds on their travels.
RELATED ARTICLE: Utah's Freezing Stormy Weather Caused Numerous Casualties to Waterbirds Flying for Migration
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