An analysis of more than 11,000 birds struck dead by a single building's windows shows turning lights off during migration makes a big difference.
Research indicates that up to 1 billion birds may be killed per year in the U.S. alone due to window collisions. Birds hit buildings at all hours during the day and night. At night migrating birds can be distracted by bright lights in our cities. During the day the problem is reflection or other confusing aspects of glass.
The increased use of glass in our modern buildings, including large expanses of highly-glazed or ultra-clear glass, presents a serious hazard for birds. Most birds don’t perceive glass as an obstacle. Instead they see the things they know and need, such as habitat and open sky, reflected in the glazed surface or on the other side of one or more panes of glass.
Artificial lights and skyglow around buildings can be fatal to migrating birds. Some are casualties of nighttime collisions with windows and walls. Others circle in confusion until dawn, when they land and are subject to other urban threats. This issue impacts hundreds of species, including priority birds like Wood Thrush, Golden-winged Warbler, and Seaside Sparrow. By working with building owners, managers, and residents to turn off unnecessary lights, we can help minimize the impact on birds.
Reflective and Transparent Surfaces
During daylight hours, shiny glass exteriors, internal plants near windows, glass corners, and greenery close to buildings can all be deadly as birds are unable to distinguish reflection from open flyway. Window collisions are one of the leading direct human causes of bird mortality, with a recent study estimating that up to one billion birds are killed annually in the U.S. Birds need strong clues on or around glass to warn them that it’s there.
Learn about what Audubon chapters, centers and programs across the country are doing to make buildings safer for birds, both day and night, as we consider the hazards that artificial light at night and glass pose.
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Cities participating in Lights Out. Please check back for updates and notify staff if you see that updates are needed.
Birds need strong clues on or around glass to warn them that it’s there. Learn more about collision prevention solutions.