Fixing the Pane Point

One woman’s mission to save songbirds from their greatest man-made threat: windows.

Imprint left on a window after a bird collision

Credit: Chuck Schug Photography/iStock

Christine Sheppard took any workaholic’s logical next step before retirement: She started a new job.

Sheppard, who has a PhD in evolutionary biology and ecology, retired early from the Wildlife Conservation Society’s Bronx Zoo in New York City, where, as head of the ornithology department, she propagated endangered bird species. In 2009, she accepted a lead role with the American Bird Conservancy to protect migratory songbirds like warblers, thrushes, and orioles from one of their greatest threats—windows. Yes, windows. Experts estimate that each year in the United States alone, hundreds of millions of birds glide right into glass panes and die.

Skyscrapers often take the heat for bird collisions, but a study published by scientists at the Smithsonian found that birds are far more likely to fly into the windows of shorter buildings. Specifically, low-rise buildings account for 56 percent and homes for 44 percent of annual collision fatalities (339 million and 253 million bird deaths, respectively). Meanwhile, high-rise buildings kill just over half a million birds per year—less than one percent. In other words, Freedom Tower isn’t the biggest problem. A four-story suburban office building with mirrored windows, on the other hand, is a death trap. Same goes for our home-sweet-homes.

“In fact, every home in the United States kills, on average, between one and ten birds annually,” Sheppard says. ”This means we can all help out.”

Sheppard points out that buildings with large panes of glass are a relatively new phenomenon. Yet it’s clear that our appetite for picture windows and beautiful views won’t disappear. So Sheppard approaches the problem with a scientist’s insatiable need for data, an engineer’s instinct for solutions, and an activist’s messianic zeal to spread her message. “When I started, there wasn’t a lot of available science on how to construct bird-safe glass,” she says. “There were just a lot of recommendations from bird lovers who were upset at the staggering number of birds dying every year.”

Christine Sheppard at the testing tunnel
Credit: Photo by William Haffey

Fast-forward several years, and the research to reduce bird fatalities has grown exponentially, thanks to Sheppard and her collaborators at the Powdermill Avian Research Center in southwestern Pennsylvania. The study subjects at the center have been netted, banded, weighed, and sexed. Researchers place the birds in a long, dark tunnel, knowing they instinctively will fly toward the light to escape. The tunnel’s opening splits into two halves: One side has a transparent window that serves as the control; the other―say, a window with a stripe pattern―is the variable. A net at the end of the tunnel stops the birds before they hit the glass, and they are then released. (See how it works in this video featuring Sheppard.)

“We need to run these tests so we can talk to architects about the relative threat values of different materials,” Sheppard says. “It turns out that birds, by virtue of having eyes on the sides of their heads, are very good at seeing to the side and behind them, but they have little depth perception, and a relatively strong signal is needed to focus their attention ahead, as they often fly toward sky or clouds. They’re like a teenager riding a skateboard while texting: Yes, he’s moving forward, but he’s not aware of what’s ahead.”

Her research has shown several paths to reducing bird collisions without sacrificing much. “We’ve found that covering as little as 5 percent of a window’s glass can significantly reduce bird strikes,” Sheppard says.

Screens, grilles, and shutters work wonders. Frosted glass, window film, and taped or etched stripes and dots—placed either two inches apart horizontally or four inches apart vertically—all significantly reduce collisions as well. (Sheppard calls the latter solution the two-by-four rule.) “Birds fly through shrubbery and leaves of trees so they are excellent at calibrating their body’s ability to make it through various small openings,” Sheppard says. “If they perceive the opening as too small, they won’t try it, and they will interpret two-dimensional patterns as real barriers.”

Ellen Rudolph is a psychologist and conservation photojournalist who routinely discovered felled birds beneath the oversize windows of her log cabin in the Great Smoky Mountains. Sheppard recently suggested that she use parachute cords marketed as Zen Wind Curtains. “Tape is fine for small windows” but impractical for large ones, “and screens are only cut to standard sizes,” Rudolph says of the challenges she faced in making her place bird-safe. “Fortunately, Christine knew of something for a house like mine that has huge custom windows.”

Acopian BirdSavers’ Zen Curtains installed on the windows of Ellen Rudolph's cabin
Credit: Photo courtesy Dr. Ellen K Rudolph

But why make such a fuss for small birds? First off, they’re integral to the health of our environment. According to research published by the American Ornithological Society, birds provide pest control, seed dispersal, nutrient cycling in the soil, and plant pollination, among other services. They also play a key role in our own health.

“It’s in your self-interest to protect the birds,” Sheppard says. “If you value clean air and clean water, then you need these small birds. As the weather gets warmer, you want birds to eat mosquitoes. You want them to gobble up bugs carrying tropical diseases. You want them to eat crop pests so we spray fewer chemicals on our food. Birds help farmers keep costs down. If they eat bugs carrying diseases, they keep medical costs down. In that way, not only are they integral to keeping the ecosystem healthy, but they provide economic value for their services.”

It’s also important to remember that many of our biggest cities are smack-dab in the middle of migration corridors, such as the Eastern Seaboard’s Atlantic Flyway. Each spring, millions of birds wing their way over (and hopefully not into) our homes as they return from wintering grounds in Mexico, Central America, the Caribbean, and South America to their northern breeding grounds.

“Our cities don’t need to be deserts or minefields for wildlife to navigate around,” says Sylvia Fallon, director of NRDC’s Wildlife Conservation Project. “They can even be a stopping ground for broader wildlife on migration patterns.”

Sheppard searches high and low for audiences receptive to her bird-conservation gospel. She addresses legislatures and government officials to draw up new city-planning ordinances. The movement has traction. Several cities in Silicon Valley, as well as counties bordering the Great Lakes, have written bird-friendly guidelines for new construction. Sheppard also teaches classes for architects, works with zoos around the country, and writes trade magazine articles for architects, engineers, and building managers on the topic of bird-friendly structures.

“I’m thrilled with the parachute cords,” Rudolph says of her wildlife-friendly abode. “They’re beautiful when they sway in the wind, and I haven’t had a single bird collision since I installed them six months ago. How’s that for results?”

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