Bird vs. Window: Windows 900-Some Million; Birds 0

Cedar Waxwing at rest.
Cedar Waxwing at rest.

In the battle of bird vs. window, the birds are getting “skunked”.

Perhaps something like this has happened to you? You are in your east-facing kitchen making coffee early on a nice spring morning. The sun is just coming up, birds are at the feeder, just off the patio, 12-15 feet from your kitchen window, enjoying their equivalent of breakfast.

There’s a sudden flurry of activity outside, you see a streak as something flies past, followed by several “thuds” on the window. A Cooper’s hawk, also ready for breakfast, spotted easy prey at the bird feeder and zoomed in for a meal. While the hawk was unsuccessful– didn’t catch a single bird—the bad news is that in fleeing, the birds at the feeder mistook the reflection of your window for open space, and flew directly into the glass.

You rush outdoors to find three birds lying on your patio, stunned but alive. You gently move them off the patio into the grass where you hope they’ll be able to shake it off and return to feeding. And when you get home after a day at the office, the birds are gone. But there is a neighborhood cat that’s always lurking, plus raccoons and a dog in the unfenced yard next door. You don’t know if the birds made it or not.

The next-door neighbors don’t have a bird feeder, but do have three mountain ash trees in their front yard, and big west-facing windows on the front of their house. They’ve lost several birds this spring to those front windows. Cedar waxwings feast on the mountain ash berries, then fly into the windows. Between the two houses, maybe a dozen (12) birds have struck windows in the past week alone. It seems like a lot of birds.

What about larger buildings? Do birds hit those windows? More and more high-rise structures are covered with glass these days.

Is the number of birds lost due to window strikes significant?

In Bird Meets Window, Window Never Loses: The Numbers
In cities where downtown areas are populated with high-rise office buildings and dwellings, the number of bird strikes reaches into the many thousands every year. The U.S. Fish and Wildlife Service  says that 97 million to 976 million birds die annually from collisions with building windows. That information came from a 2002 fact sheet. The number of high-rise buildings has markedly increased in the years since that report.

Those of us living in mid-sized cities know it doesn’t take a high-rise building to kill birds. A reflective surface is all that’s needed to allow a bird to mistake glass for open flying space.

Why the Bird-Glass Conflict
Birds fly into windows based on several situations. They are fleeing a predator bird such as a hawk and from a setting where the prey bird is feeding a certain distance from glass. The distance between bird feeder and glass allows the bird to accelerate to a speed that proves deadly upon impact.

At times the sun’s angle on a window causes maximum reflection, so that instead of seeing a solid surface, birds see trees, plants, or whatever landscape is behind them in the reflection of the window they are approaching. Or the bird sees nothing but sunlight. At certain times of the year the sun angle, and thus the reflection is more deadly. In addition, there is evidence that during migration, birds become tired, undernourished or ill and are less able to discern certain dangers, like reflective surfaces on buildings.

The Good News
Bird-window collisions can be prevented, no matter the size of the building. And a variety of interventions can be applied, from small and homemade, to large, industrial-sized treatments.

The main goal, birdwise, is to block or break-up the reflective surface of the glass. If the windows are older, you may be able to do this with interior shades or blinds. When closed, the blinds can help birds identify the window as an object or solid surface.

Homemade Remedies
However, especially for modern glass that is more highly reflective, exterior window treatment is essential to break up the reflection. Remedies such as spraying kitchen oil on or tempera painting or whitewashing the exterior of windows has been tried with some success. Covering the exterior of windows with homemade or purchased strings of birdfeathers, for you collecting types, is reported to have some success, while others have covered the exterior of windows with branches and twigs. Here are some things you can try at home.

And this site has links to purchase a wide variety of exterior window treatments. Remember that small decals are considered the least successful—cover the entire surface to save the most birds.

There are exterior window films that can be applied, and applying tape in horizontal and vertical stripes, using the 2 x 4 rule, stripes being 2” wide and a maximum of 4” apart, has been found successful for some.

If you feed birds, experts recommend moving bird feeders closer to windows, the thought being that birds that hit a window from just inches away, will most likely not be hurt.

For Best Results
The most successful window treatment, reported to have 100% success, is covering windows with netting, such as is used to keep birds away from fruit trees and shrubs. This method is recommended by Dr. Stanley Temple, Ph.D., Beers-Bascom Professor Emeritus in Conservation, University of Wisconsin and Senior Fellow, Aldo Leopold Foundation, as well as the Cornell Laboratory of Ornithology.

The netting must be applied properly, however, to save birds lives. Dr. Temple says to string the netting so that it is 12” from the glass surface and with tension. The netting not only breaks up reflective surface but also serves as a trampoline of sorts; birds hit it and bounce away from the glass. The Audubon Society also mentions the use of netting for success in preventing bird deaths.

About High-Rise Buildings
Larger buildings are thought to be disorienting for birds not only due to reflective glass surface, but also because they often have interior lights on at night. The brightly lit buildings attract or confuse birds during nighttime hours. A number of major cities have begun to participate in the FLAP program, where they pledge to turn off interior lights, even rescheduling nighttime cleaning , to help prevent bird losses. Details about that program can be found here.

What Have You Tried?
If you’ve had problems with birds colliding with windows, either at home or at work, and have done something to prevent these collisions, let us know about it. What have you tried? Was it successful?

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Kari Kenefick

Kari Kenefick

Kari has been a science writer/editor for Promega since 1996. Prior to that she enjoyed working in veterinary microbiology/immunology, and has an M.S. in Bacteriology, U of WI-Madison. Favorite topics include infectious disease, inflammation, aging, exercise, nutrition and personality traits. When not writing, she enjoys training her dogs in agility and obedience. About the practice of writing, as we say for cell-based assays, "add-mix-measure".

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