Windows Pose Life Threatening Threat to Birds


Mary Beth Breckenridge


(From Animals In Print Newsletter)

It's a stomach-turning sound to anyone who's seen or heard a bird fly


into a window at full tilt. Birds can't distinguish glass from open


air, and that lack of judgment can injure or kill them.

No one knows how many birds whack into windows each year, but


researcher Daniel Klem Jr. estimates the U.S. death toll at 100


million to 1 billion. That's as much as 5 percent of the bird


population after the breeding season, and he suspects the actual


number is even higher.

``Almost every structure on this planet has a piece of glass in it,''


he said, and every one of those windows represents a potential hazard


to birds.

Klem, an ornithologist at Muhlenberg College in Allentown, Pa., based


his estimate on research indicating one to 10 birds are killed each


year for each building in this country, on average. And that doesn't


count all the birds that end up with sore noggins or battered beaks


from their nonfatal run-ins.

The problem, Klem said, is that birds don't perceive glass as an


object. They see the sky reflected in a window, or they spot habitat


through another window beyond, and into the glass they go.

Bird watcher Bill Thompson III has seen as many as five birds a day


killed against the windows of his house, which sits on a ridge in a


rural area near Whipple in southeastern Ohio. His wife has a windowed


studio that overlooks a brushy area, and especially during spring


when the young birds are starting to fly, ``we get thunk, thunk,


thunk, thunk,'' said Thompson, editor of the magazine Bird Watchers


Digest and a director of the Ohio Ornithological Society.

About a quarter of North American bird species have been known to fly


into windows under a variety of circumstances, Klem has written. Some


are trying to outrun a predator. Some are migrating. Others are


looking for food, water or shelter.

Most strikes happen in winter, he said, when birds visit feeders in


large numbers and often run into windows on their way to or from


feeding stations. The problem gets the most attention during spring


and fall migrations, however, because window accidents and their


victims are most noticeable then.

Mating season is a time for a less dangerous kind of bird strike,


when a male bird -- often a cardinal or robin -- sees a reflection of


itself and think it's competition, said Damon Greer, a wildlife


biologist with the Ohio Department of Natural Resources' Division of


Wildlife. The bird will peck at the glass persistently to try to get


at the intruder, sometimes for weeks on end. The bird rarely suffers


anything worse than the occasional bloodied bill, Greer said, but the


humans on the other side of the window can be driven to distraction.

Klem has argued for changes in building design to reduce bird


strikes, including angling first-floor windows downward so they


reflect the ground instead of the sky. So far, he said, he's gotten


little heed from the building industry.

That could be changing, though. Audubon magazine wrote in its March


issue that Klem's work has influenced construction projects including


a science building at Swarthmore College, which will have windows


with dots of opaque glass to discourage bird strikes. And the New


York City Audubon Society is campaigning for bird-friendly design in


any buildings that rise on the World Trade Center site.

In the short term, however, challenges remain. Thompson, for example,


tried to have windows installed at a downward angle on a construction


project at his farm and discovered that doing so would void the


manufacturer's warranty.

Avoid bird strikes

Bird experts offer other suggestions for preventing bird strikes,


such as stretching netting over windows to cushion the blow or


hanging objects just outside to break up the birds' view. None is


foolproof, however, and homeowners often object if they obscure the


view, block the sunlight or look unattractive.

Still, Thompson believes they're useful at least as short-term


measures for times when bird strikes are prevalent, such as migration.

``There are some drawbacks to every single one of them,'' he said.


``... You have to balance utility with making them (windows) as safe


as possible for birds.''

http://www.all-creatures.org/aip/

Posted on SHARE Yahoo group Nov. 12, 2004