The soft but sickening "thud" sent out a wave of impacts. Conversation, typing, and higher-level thinking stopped. From four corners of the office, heads instinctively turned toward the sound. Bright morning sunshine streaming through the window illuminated nothing unusual, though.
With a mix of hope and dread, I opened the back door and scanned up and down the patio. Nothing. I sighed with relief and stepped back inside.
I’d been expecting to find a small bird — lying either lifeless or stunned and glassy-eyed — at the base of the large row of windows that face the Museum’s back yard. Low-angled sunlight in the spring, in the fall, and early in the day, sneaks under awnings and tints the glass of our windows with stunningly accurate reflections of trees and sky. When little birds try to fly into that scene, they get a painful — and often deadly — surprise.
Birds can collide with windows in any season, but I’ve always noticed an increasing number of those sickening thuds in spring. As waves of migrating birds head north, we see both a huge increase in the number of individuals, and an increase in birds who are new to the neighborhood and more likely to be hoodwinked by windows.
According to the Humane Society, roughly half of the birds that hit windows succumb to their injuries or are killed by predators while they’re vulnerable. The "thud" I heard was from one of the lucky ones who flew away. An estimated 1 billion birds die this way each year.
From the number of calls and emails I get on this topic, I know that these bird deaths weigh heavy on the hearts of many. Not only is it distressing to find feathered corpses outside your home, or to watch the life go out of something so innocent and delicate, but headlines tell us that birds are in global decline due to habitat loss, climate change, and more. Each small life counts toward the whole.
Now that warm days are turning even window washing and yardwork into attractive tasks because they give us excuses to get outside, it’s a good time to think about making your windows better for birds.
Window screens that go on the outside of the glass are one of the best tools for preventing collisions. Not only do they break up the reflection, they also act as a safety net. If your windows didn’t come with bug screens, you can use bird netting from a garden store (meant to keep robins out of your strawberries) instead. Just make sure to pull the netting taut like a trampoline, and keep it at least 3 inches off the window so the birds don’t bottom out.
A purely visual grid can also work well. Using tape, soap, tempera paint or paint pens, you can add designs to your windows that make the glass visible to birds. If you’re feeling artistic, an intricate doodle would do the trick. Otherwise, using a level and a yardstick, you can simply draw lines.
The key is to make the spaces between the lines small enough that birds don’t try to squeak through. For best results, vertical lines should be no more than 4 inches apart, and horizontal lines no more than 2 inches apart. If your casualties include hummingbirds, then use the 2-inch measure all around.
While not practical for everyone, you could make the designs permanent by etching or sandblasting them directly onto the glass. If you’d rather use decals, they need to be just as densely spaced as the grid in order to be effective. A company called Collidescape makes grids of dots and one-way transparent film that can do the job.
But those single, elegant hawk silhouettes have been shown not to work. Likewise, past recommendations about how to safely space bird feeders away from windows haven’t stood up to testing.
You can also combine the ideas of a grid and a screen and make “zen curtains.” Basically a grid made of cords; they hang down over the glass on the outside of the window. They can be easier to install than paint, longer lasting, and can be aesthetically pleasing. I’ve seen them made from sparkly string with tiny mirrors attached, and the effect was delightful! A simple internet search will turn up both commercial and DIY versions.
Not every window or every homeowner can accommodate these ideal modifications, though. Using a simpler option, or a combination of techniques, is still helpful.
At the museum, we often tape a single length of curling ribbon at the top center of each window. As the ribbon blows and bounces in the breeze, it helps to deter birds. Awnings, external sunshades and shutters can also minimize reflections. Having flowers and shrubs at the base of windows can encourage birds to dive in for shelter instead of trying to fly through to escape from a predator.
Making changes indoors can have an impact, too. Blinds, shades, or even sheer curtains on large windows change the reflection quite effectively. And my favorite recommendation is one of the easiest: letting your windows stay slightly dirty can cut down on the realism of the reflection.
Recent research found a positive relationship between the diversity of bird species in a neighborhood and the life satisfaction of people who live there. Add that to the reduction in those sickening thuds, and bird-proofing our windows feels like a great way to increase happiness this spring.
Emily Stone's award-winning second book, "Natural Connections: Dreaming of an Elfin Skimmer," is available to purchase at cablemuseum.org/books, or order it from redberybooks.com to receive free shipping.
For more than 50 years, the Cable Natural History Museum has served to connect the public to the Northwoods. The museum is now open with the "Mysteries of the Night" exhibit. Connect with the museum on Facebook, Instagram, YouTube and cablemuseum.org to keep track of its latest adventures in learning.