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Birds and Windows

One billion birds die each year in the United States due to collisions with windows.

Orange-crowned Warbler - Mary Coolidge
Orange-crowned Warbler - Mary Coolidge

Up to one billion birds die each year in the United States due to collisions with windows. Window  strikes are among the top three human-related cause of bird deaths, along with cats and habitat destruction. Research shows that 54-76 percent of window collisions are fatal; stunned birds that fly away often hemorrhage out of sight. 

Why Do Birds Hit Windows?

Birds do not perceive windows as a barrier. They see reflections in glass as open space and fly full-speed into it. Recent data analysis shows that residential buildings (1-3 stories) account for 44 percent of window collision deaths in the United States. Low-rise buildings (4-11 stories) account for 56 percent of window collisions. Fewer than 1 percent occur at high-rise buildings. This is simply because, across the nation, there are so many low-rises and residential homes relative to highrises. 

Another cause of window collisions is male birds defending territories during mating season. They perceive their own reflection in glass as a competing male, and attack it repeatedly in an attempt to drive the intruder off. Robins and Flickers commonly exhibit this kind of behavior. Less common causes of window strikes are disorientation due to disease and intoxication from eating fermented berries.

How to Prevent Window Strikes

Birds are accustomed to navigating very small spaces in trees, vegetation, and the built landscape. Therefore, to interrupt reflections, markers need to be distributed across the entire window, spaced 5 to 10 centimeters apart. This can be accomplished a lot of different ways! 

DIY Approaches:
  • Place bird feeders within 3 feet of or farther  than 30 feet away from windows.
  • Attach decals (available at the Audubon Society of Portland's Nature Store and other bird shops) directly to the outside of windows to break up reflections. Decals must be placed much more densely than the manufacturer suggests, ideally following the 2x4 rule.
  • If you have a particularly persistent and aggressive male, try affixing various objects directly to the outside of the window. Closing the shades or curtains will not work since the bird will still be able to see its reflection. Mylar tape, colorful streamers, wind socks, and fine netting can all be effective short-term deterrents. The movement of these objects will often frighten birds away. You may also try covering the outside of the window entirely with plastic. Attach to the top of the window and let it hang free at the bottom. Most breeding cycles only last for a few weeks, so you will not have to keep your window covered permanently.
  • In the spring and fall, bright city lights confuse birds who migrate during the night by luring them into cities and obscuring their navigational aids. Once trapped in the windowed maze of the city, they may hit windows directly or circle buildings until they collapse from exhaustion. To help prevent window strikes during migration, make sure your exterior light fixtures are well-shielded and are not producing dazzling glare. Draw blinds or curtains to reduce light spill that contributes to sky glow. Learn about LightsOut Portland. 
  • Trees or shrubs planted very near to and in front of windows may help interrupt or cut down reflections. This can help make the window less apparent to birds. 
  • Let your windows stay dirty: they’re more visible that way!
  • Move interior houseplants away from windows where strikes are common.
  • Densely apply patterns or decals to the outside of windows (5-10 cm apart); stretch thin netting over the outside of the window; apply cords to the outside of the window: www.birdsavers.com
  • Apply window film patterns or decals to the outside of windows. Decals must be placed 5-10 cm apart. Resources include: ABC bird tape, etched glass decals, decorative decals, adhesive dot pattern, solyx window film, ultraviolet decals, Bird’s Eye View and CollidEscape

What To Do If A Bird Strikes Your Window

Not all strikes are fatal (though upwards of 54-76 percent are). Sometimes a bird may be temporarily stunned. The Audubon Society of Portland's Wildlife Care Center recommends placing the bird in a small box. Line the box with a towel and place half the box on a heating pad set on low. Give the bird a small bowl of water, but no food. Do not force the bird to drink. Place the box in a warm, quiet place. Check the bird in one hour. If the bird is alert, active and able to fly, release it immediately. If the bird is still having trouble, bring it to the Wildlife Care Center or a wildlife rehabilitation facility near you. The Wildlife Care Center can be reached at 503-292-0304.

Additional Resources

Tips for reducing window strikes at home

You Can Save Birds from Flying into Windows (pdf) - American Bird Conservancy brochure   

Birds and Windows Brochure (pdf)

Windows in downtown Portland - Mary Coolidge
Windows in downtown Portland - Mary Coolidge
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