Window Collisions

Bright Lights, Big Cities: Lights & Windows are Deadly Hazards for Birds

At least 100,000,000 birds are killed and even more are injured every year across North America by collisions with windows. Ornithologists have been studying this phenomenon for decades and their findings are very conclusive: birds simply do not recognize glass as a barrier . During daytime, birds often fly head-on into windows, confused by the reflection of trees or sky. This is a common occurrence even in the suburbs at homes and glassy office campuses. Of the birds that suffer head trauma, over half die.



Additionally, scientists have observed that at night the bright lights of buildings seem to confuse birds, especially during cloudy, foggy or rainy weather. Large masses of birds have been photographed during the night at one of Chicago's skyscrapers, the birds continually circling and battering the building lights. By dawn the birds are either dead or seriously injured. These birds were migrants on their twice-yearly, night-time migration. During some weather conditions and at certain "killer" buildings, the death toll can be in the hundreds per day.





Birds are attracted to the lights not only at the tops of the buildings but also to the lights in mid-level office windows and ground level lobbies and atriums. Recent research by ornithologists at the Field Museum of Natural History confirmed that simply turning off bright lights or closing blinds reduces bird deaths by 83%.



You can make a difference

Because of the enormity of the situation (after all, lights and windows are everywhere) many people find the problem too daunting to tackle. Don't be discouraged: there are many easy actions you can take at your home and office to significantly reduce the number of birds killed.



Even not washing the windows during the migration months helps keep the reflective qualities low and, thus, can help reduce bird injury and death.



And, please talk to the owners, managers and maintenance staff of your office building about what can be done to make the facility bird-friendly. Make them aware of the meaningful contributions they can make to save the lives of hundreds or thousands of birds each migration season.

Additional Information

More tips and information about birds and window collisions can be found on the

Chicago Bird Collision Monitors website. CBCM is an organization that works in the Chicago area to rescue migratory birds injured from striking buildings, and to mitigate the risk of bird-building collisions by educating the public and working with building managers to find solutions. CBCM has a page on avoiding window collisions and a listing of products to make your windows safe.

The American Bird Conservancy, ABC, has an extensive website on bird collisions and glass including information on why birds hit glass, a bird-friendly building design guide, and bird-friendly window solutions.

Lights Out is a voluntary partnership between the Building Owners and Managers Association of Chicago, and the Chicago Department of the Environment, working to see that virtually all Chicago’s tall buildings extinguish their lights during the migration season. The Lights Out website has information about the Chicago program and a “Tool Kit” that other cities can use to emulate our success.