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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 percent 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.

It's 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.

— Text by Dave Mehlman, Cool Green Science Blog

Window glass: Silent bird killer?
Windows take a toll on birds -- killing up to 1 billion a year in North America. Conservancy bird expert Dave Mehlman gives tips on how you can help stop this d