I’d heard the sickening “thwump” sound and turned just in time to see a dazed mourning dove flying away. She’d flown into one of the large salvaged windows which make up my new greenhouse. Turns out, when the light’s at just the right angle, my greenhouse becomes a veritable house of mirrors.
I’d unwittingly created a potential deathtrap for some of the very creatures I work hard to help. This would not do.
Of course, I knew that birds and glass are a deadly combination. But I didn’t realize just how deadly until I came across the work of Dr. Daniel Klem, Jr. Klem is an ornithologist and the author of Solid Air: Invisible Killer: Saving Billions of Birds from Windows.
“The latest scientific estimates suggest that annual bird kills at windows range from 365 million to 988 million per year in the U.S., 16 million to 42 million in Canada, and billions worldwide,” Klem writes. “Even the lowest U.S. estimate is equivalent to the avian death toll from 1,215 Exxon Valdez oil spill disasters.”
Greenery & Glass
According to Klem, multiple researchers have concluded that the overall number of bird-window collisions increases in areas with combinations of greenery and glass. “Increased casualties occur at buildings with nearby vegetation in the form of trees and shrubbery that attract birds to the danger zone near windows,” he writes.
My greenhouse is positioned in the middle of my back yard—and surrounded by trees, pollinator gardens and other greenery. With so much vegetation around to be reflected by so many windows, my local birds wouldn’t stand a chance.
Read more: Invite birds to your farm with a hand-built bluebird nesting box!
Simply Stunning?
Sadly, even when we think a bird has managed to survive a window collision, they frequently don’t. Some do fly off—only to perch in some out-of-the-way spot while they try to recover. Unfortunately, many of these recovering birds are picked off by outdoor cats and other predators.
Still other post-collision birds leave the scene with internal bleeding, broken bones, brain injuries and other serious issues. They, too, aren’t likely to thrive long-term.
Bird’s Eye View
The main problem with most windows is that birds just don’t see them. With a certain amount and angle of available light, a window might look completely transparent. As the light shifts, that same window can perfectly reflect the sky, trees and other natural elements.
In either case, a bird is not likely to perceive this solid pane of glass as an obstacle.
When it comes to effectively preventing bird-window strikes, affixing a few hawk silhouettes inside your windows won’t do much good. Neither will relying on the natural accumulation of a little grime.
Instead, the outsides of your windows—in their entirety—must include some patterned visual elements. “Patterns that effectively deter bird strikes must uniformly cover the surface of the window, and the elements making up the pattern must follow the 2 x 4 rule,” Klem notes.
After much trial-and-error, researchers have determined that birds will see—and steer clear of—horizontal patterns or rows occurring at two-inch intervals. Birds will also avoid vertical patterns or columns spaced 3 or 4 inches apart.
“Effective deterrent patterns can be applied to existing windows with soap, tempera paint, tape, films and cords, strings or ribbons,” Klem adds.
Read more: Windbreaks are great for attracting birds and other wildlife to the farm.
Finding a Fix
There are a few bird-friendly businesses offering their own fixes. For instance, BirdSavers sells finished window paracord products and also offers DIY instructions. And both CollidEscape and Feather Friendly sell specialty films or tapes intended to be applied to your windows’ exteriors.
(Although these products are visible from the outside, they won’t really obscure your view from the inside looking out.)
To solve my own window-collision issue, I opted for CollidEscape’s three-quarter-inch tape in white. With a squeegee, bucket of hot water, clean rags and glass cleaner in tow, I headed to the greenhouse.
We’d had a string of unseasonably warm afternoons—temperatures were just above 40 degrees. That meant I’d be able to get the windows squeaky clean and make sure the tape really stuck.
I added vertical stripes to the outside of each window, spacing the stripes four inches apart. I’ve noticed that plenty of light can still penetrate the striping, and, from inside the greenhouse, my view is unobstructed. The tape itself should last about 10 years.
Best of all, I’m much less likely to hear that awful thwump—and I’ll be saving countless birds in the process.
