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Drivers of fatal bird collisions in an urban center
Van Doren BM, Willard DE, Hennen M, Horton KG, Stuber EF, Sheldon D, Sivakumar AH, Wang J, Farnsworth A, Winger BM
Proceedings of the National Academy of Sciences
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Building lights are a deadly lure for the billions of birds that migrate at night, disrupting their natural navigation cues and leading to deadly collisions. But even if you can’t turn out all the lights in a building, darkening even some windows could be a major lifesaver for birds.

Our research, published June 15, 2021 in PNAS, found that over the course of 21 years, one building sustained 11 times fewer bird collisions during spring migration and 6 times fewer collisions during fall migration when only half of the building’s windows were illuminated, compared to when all windows were lit.

The factors that had the strongest effect on bird collisions were the intensity of the migration (more birds migrating = more collisions), the wind direction (westerly winds = more collisions), and area of illuminated windows (more surface area lit = more collisions).

Selection of birds found at McCormick Place, from the scientific collections of the Field Museum. Image courtesy of Karen Bean, Field Museum.