Window Strikes Kill about a Billion Birds a Year

Every backyard birder’s heart sinks at that “thunk” against a window, the unmistakable sound of a bird flying full tilt into glass. We dash to check. Did the bird strike only a glancing blow and fly on? Is it in a heap on the ground, dazed, a target for predators? Or, fear of all fears, is it dead?

PictureBirds don’t see houses as buildings with windows. They see obstructions with passageways. Of course they recognize a solid wall for what it is. But that window, reflecting foliage and clouds, looks like a passageway through the wall—an avenue to another feeding territory or a means of escape from predators. And so, thunk, into the “passageway” they go.

Recent reports from area backyard birders tell the story: Yellow-bellied Sapsuckers, Red-headed Woodpeckers, Indigo Buntings, Cedar Waxwings, Ruby-throated Hummingbirds, and, especially it seems, Mourning Doves—all fatally attracted to “passageways.”

And the plea is the same in every report: What can we do to keep the birds from flying into our windows?

According to Dr. Daniel Klem, Jr., a former Southern Illinois University ornithologist now at Muhlenberg (Penn.) College, collisions with glass kill upwards of a billion birds annually. Migratory birds crash into tall buildings during night flights, and, as Klem notes, a single skyscraper can kill 200 birds in a single night.

PictureIn fact, only habitat destruction kills more birds than do windows.

PictureResidential windows, however, according to Klem, “continue to kill the most birds for the simple reason that there are so many houses.” Northern Cardinals, Eastern Bluebirds, American Goldfinches—any of our favorite yard birds—startled by a cat, hawk, or other danger that provokes their frantic flight, flee headlong, smack into the reflection.

In full flight, a bird strikes glass with fatal force, breaking wings, beak, and/or neck.

Experts agree: Any solution involves breaking up the reflection, eliminating the “passageway.”

The traditional suggestion of adding plastic stick-on hawk decals gets little support from Klem and others who had little success with this method. The problem with decals, of course, is that birds don’t look at decals and think, “Hawk.” It’s just a small obstacle in the “passageway” around which they must fly. In fact, one friend reported a Mourning Dove crashed into their window precisely between two hawk decals.

But since it’s all about breaking up reflections, according to the National Audubon Society, decals of any shape, like hawks, dots, butterflies or stars, will work—but only if spaced uniformly, two to four inches apart, over the window’s entire surface, thus transforming the window into “an obstacle birds will see and avoid.”

Donald Burton, director of the Ohio Wildlife Center, says there is “no perfect solution” for homeowners “other than covering the entire surface of a window with netting,” a reasonably satisfactory method that is probably less obstructive than regular window screen.

PictureOther suggestions:
Place feeders and birdbaths within three feet of windows so that should birds fly into the window they will be moving too slowly to cause serious harm. Or, conversely, place feeders and baths a safe distance from windows so that departing birds have adequate space to avoid windows.

Since the ultimate goal is to break up reflections, try vertical exterior tape stripes placed about 12 inches apart. Or hang obstacles like tree limbs, strips of cloth, or feathers on a string in front of the glass. Or arrange interior vertical blinds with the slats half open.

But for those of us who don’t like to do windows, here’s a thought: Dirty windows don’t reflect. Excuse enough for me