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Windows: Indiscriminate Kilers

Windows: Indiscriminate Kilers

You’re sitting at the dining room table, reading the paper and glancing occasionally at your bird feeders, when SMACK!, something slams into the window. It’ s happened a few times in the past, so you know what you’ll find, you just don’t yet know whether the victim will be a cardinal, mourning dove, Cooper’s hawk, or perhaps a migrating ovenbird.

These fatal collisions don’t happen often at any one house, so most of us don’t address the problem. Even at Chippewa Nature Center, our efforts to reduce the number of birds killed when flying into Visitor Center windows had for years gone no further than putting up a few hawk silhouettes to break up the reflection of the glass.

So a dozen die here, and a few die at your house–it doesn’t sound like a serious problem, does it? The numbers add up, though, house by house, skyscraper by skyscraper, until each year, over one BILLION birds die in window collisions. And that’s a conservative estimate, according to Dr. Daniel Klem, who has studied this conservation issue for nearly three decades. Klem is a research ornithologist from Muhlenberg College in Allentown, Pennsylvania. He studies not just the scope of the problem, but viable solutions as well.

The basic problem for birds is that they see trees and sky reflected in windows. They don’t recognize the window as part of a building, and continue ahead at full steam. Even at times when there is no reflection, windows placed across from each other, as with the River Overlook of our Visitor Center, create the illusion that birds can fly through to what they see on the other side.

Window kills occur on all sizes of windows, all sizes of buildings, and in all four seasons. So what can you do to lessen the impact (literally!) of windows at your home or nature center? Klem has studied many possible solutions, including placing bird feeders closer to windows, using decals to break up reflections, and architectural and glass style options such as angling windows outwards, using glass with imbedded dots (resulting in a frosted appearance), and designing buildings with deeply recessed windows.

The most commonly used but least effective method is placement of decals on “problem” windows. The problem is, birds are used to dodging through forests, seeking out very narrow gaps between sturdy tree trunks. Unless decals are literally no more than four inches apart, birds still hit the reflective space in between them.

Window screens are quite effective, if you are willing to sacrifice the sharp image you get through a screen-free window.

Another effective solution for windows used for viewing bird feeders is to move at least some of the feeders right up to the windows. Klem’s research found that if feeders are within three feet of a window, mortality from strikes is nearly zero.

The greatest potential for solving the problem appears to lie in architectural design and window manufacturing arenas. Glass with tiny imbedded dots spaced only a few inches apart is proving to be very effective at reducing, or eliminating altogether, window strikes. If you have the luxury of starting a design from scratch, use windows angled outwards at 20 degrees or more, so the reflection is of the ground, not trees and sky.

Contact Klem at klem@muhlenberg.edu to arrange a presentation of his research or assessment of buildings at your nature center. For further information on this topic, check out www.birdsandbuildings.org.