Window Glass: Silent Bird Killer?

Birds just do not get the concept of “glass.” We’ve all surely had the experience of having a bird fly into a window at our home, office or school, usually with unfortunate consequences for the bird. But have you ever stopped to think about how widespread this phenomenon is and how many birds it might be killing annually?

Dr. Daniel Klem Jr. of Muhlenberg College is one person who has thought about this problem and done much to bring it to the attention of bird conservationists in the United States and elsewhere. He has compiled an extensive amount of information, available at his Birds and Windows website.

Estimates are that between 100 million and 1 billion individual birds are killed annually by collisions with windows in the United States alone — I see no immediate reason why these figures would be erroneous. Klem has documented more than 270 different species of birds killed at windows in the United States and almost 800 species worldwide; the former represents more than 25% of the species known to occur in North America north of Mexico.

Potentially any bird species that occurs in urban, suburban or rural environments could be affected, regardless of age, sex, or conservation status. Species occurring in wetlands, oceans or in areas far from human habitation are less at risk. Some of the more commonly killed species, as shown in Klem’s earlier work, are American Robin, Dark-eyed Junco, Cedar Waxwing, Ovenbird, and Swainson’s Thrush.

What can be done about this phenomenon? If there’s one thing to which “act locally” applies, this is it — we can all take action at our homes, offices and schools to reduce and eliminate this major problem.

Its not always easy and may involve some sacrifice of views out the window, but it’s worth it in terms of reducing this deadly menace to birds. Here are several things you can do to deal with window collisions:

  1. Move bird feeders, bird baths and perches to within 3 feet of your window — you’ll see the birds better and they can’t fly fast enough to get hurt.
  2. Collisions are caused by birds trying to fly through glass or because they see reflections from the outside — so do what you can to break up or eliminate this by placing decals or strings on the outside of your windows, separated by no more than 4 inches vertically and 2 inches horizontally.
  3. Use screens, films or other coverings on your windows that eliminate reflections — or use bird-safe glass.
  4. If constructing new windows, consider angling them 20 to 40 degrees from vertical.
  5. When installing new landscaping, consider placing trees, shrubs, water features, and other bird attractants well away from windows.

One new and ongoing effort to address this problem that I find very intriguing is a proposal to include “bird safety” in future iterations of building certification in the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) system. Good references on the subject of bird collisions with windows are maintained by, American Bird Conservancy and the Birds and Buildings Forum. Please consider implementing some of these actions and let me know how they work out.

(Image credit: readerwalker/Flickr through a Creative Commons license.)

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  1. As of Jan. 31, 2010, the city of Toronto has made bird-friendly design a requirement in most new buildings. A North American first. Like the above, the rules have been incorporated into the city’s Green Development Standards.

  2. Wow. I had no idea so many birds were dying from something as simple as a window. How does one go about making windows bird-friendly?

  3. it is important to bring about awareness of methods to prevent injury of birds. It is also important to support wildlife rehabilitation societies that can rehabilitate injured birds/animals. Calgary Wildlife Rehabilitation Society in Calgary, Canada is a volunteer driven society working with veterinarians treats and releases over a thousand birds and animals injured or orphaned in the city every year. please consider a donation to a rehabilitation society in your area to help injured wildlife.

  4. Is placing your bird feeder/perches within 3 feet of your window AND placing shrubs, water features, and other bird attractants far away from the window contradictory??

    Thank you!

  5. Aaron H – I think the 2 landscaping methods reflect solutions to different problems. But they probably ought to say place these within 3 feet or farther than 15 feet, ie using both concepts. In my experience most birds that run into windows are “fleeing” from a predator, usually a hawk, and are scattering from the tree/feeder area. They seem to have trouble looking in the rearview mirror and seeing forward at the same time in that distance. Landscape further away gives them time to manuver and see the surrounding house structure. Landscape closer means they’ll usually start out flying the other way.

  6. The link on this page to Klem’s web page is invalid.

  7. it is really a bad thing the dying of birds in a so really mekes me unhappy.

  8. With us it’s a cardinal. We’ve tried all your tips;
    researched it, had 3-m put on the windows, hung glitter strips, cords that blow, I’ve made big posters of owls, posters of scary faces, put up sheets, covered the whole windows and still he comes. His mate sits in a nearby tree and just watches him. It’s been three years. He has no crown feathers, a quite rough and tumble looking bird. We’ve found other birds on our steps that didn’t make it, not a lot, but this one cardinal just keep flying into our window. You can hear him knock every time he hits. We’ve had many attempt to explain it but have had others tell us they have problems with the cardinals also. We live in metro Atlanta in lots of woods. I know it’s a problem in metro areas. We’ve had it on occasion at other homes for many years.
    We love our birds but have come to the conclusion that he hit once too hard!

  9. On the feeder-watch windows of the Newman Wetlands Center in Clayton County, GA, I’ve attached dead branches on the outside window frames with flagging tape streamers Those windows seem to be having far fewer hits…and they also give us good looks at the insects and tree frogs that use them.

  10. I installed inexpensive window screens over my north facing windows. I simply stapled the screens on the window frame with about three inches between the screen and window glass. It has really helped cushion the impact. Yes they are usually fleeing hawks, but sometimes just migrating when they fly into the window.

  11. I placed a picture of a cat on the outside of our wood house up near the peak and it seemed to scare off the flickers that were digging in the wood.

    I presume a picture of a big owl or cat on the inside of your window facing outwards, say behind the drapes at the window edge or even in the mddle low down, would tend to deter birds from flying in…Anyone know of research on this? I think its worth a try. A big color photo of a cat off a cat food bag appears good to me.

  12. I had another thought. We should habitually draw our drapes closed whenever we leave the house or head off to bed. [Its also a good energy conservation practice both winter and summer.]

  13. We have found a product that has stopped birds from flying into our windows, 90% at least. It’s called ‘WindowAlert’.
    It’s a packet of see through Decal’s with hummingbird or butterfly images. Birds can seethem better then the humane eye. We placed the decal’s in the middle of the window. If a bird does hit, it’s always lightly as if the bird saw the decal at the last minute and pulled back. No more dead birds. Also, a slightly dirty window is a good thing too.

  14. I lost 2 hummingbirds, 2 doves, and a cactus wren to windows this past year, after putting up a birdfeeder in my backyard, including a hum feeder. I put an owl figure on my patio table and that seems to help, although there have been a few “hits” with survivors, of late.

  15. I agree with “David”. Keeping our screens on all year has helped keep the birds from knocking themselves silly on our windows in the winter. We don’t feed them in the summer.

  16. Sadly, our Homeowner Association won’t even place a protective covering over an powerful overflow drain to protect the ducks, a protected species [left unprotected]. Another form of “Silent Bird Killers”….

  17. can’t make a imagination in my mind that lots of birds die because of windows collide annually.

  18. The problem with the Cardinal mentioned above is probably that he is trying to attack his “rival” in the mirror (window). They are known to be very agressive in that way.

  19. The white static-type decals placed on the inside of windows over the entire area of glass several inches apart helps. Cats inside the window don’t even seem to phase most birds. Placing a bird feeder with suction cups on my window has helped enormously. Black plastic (use a trash bag) cut-outs of a diving hawk/falcon do some good (plastic doesn’t fade like construction paper will.

  20. Since I put the window decals on all of my windows, no accidents anymore. The decals are electrostatic, reflect ultra violet light making them brilliant visible to birds but nearly invisible to you.
    Inexpensive and I got mine from and also from
    Erika Oberst

  21. I purchased screen wire and attached it to the outside of our windows with suction cup hooks. It works well but the hooks let go after a while and I have to reattach it. Also, where I have not fitted it well, the stupid birds fly into an open space even tho it is relatively small. We have 1 feeder attached to a window and the birds will sometimes fly above the feeder into the window pane.

  22. Dave, thanks for addressing this VERY important issue! Please add links to and – they’re incredibly helpful in offering tips for residences as well as commercial buildings. Also, keeping cats inside will allow stunned birds to recover in peace; a lot of deaths attributed to cats may actually be window kills.

  23. I bought some of those WindowAlert decals years ago from a nature store in Arizona and they’ve really helped. Once in awhile somebody hits the window but not hard. The ones on the windows now have been up there for 9 years. I can see through them (butterfly shapes) but they must still reflect the light in a way that warns the birds.

  24. All of the dead birds in my yard are killed by cats.
    when a cat claws a bird, it takes a couple of hours for it to die from bacteria. (according to my Vet)

  25. I remember some office windows that had hawk decals on them that I think were placed there to cause birds to fly the other way and avoid a collision with the window.

  26. Hello ….I heard there is glass manufactue in the state of Wisconain that is developing a glass for birds. The are developing the glass for the Sear’s Building in Chicago

  27. I had no idea that the issue was that big….never would have guessed that it was killing that many birds in North America alone.

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