By Design: An Architectural Awakening Could Save Billions of Birds

As many as one billion North American birds die each year in after colliding with windows. Innovations can help them steer clear.

With its lush, tidy plant beds and outdoor benches, the office compound in Markham, a suburb of Toronto, seemed park-like on a mid-July morning. Ontario had little rain this summer; forest fires raged in provincial parks. But the trees, shrubs, flowers, and lawns of this corporate campus were damp and green. Michael Mesure stood in the center of the complex, taking stock. A few months earlier, the property manager had asked him for an assessment. “When a building contacts us, it is because there are dead birds in front,” Mesure said, pointing to a glass façade that mirrored the verdant canopy. “The birds move from tree to tree gobbling up insects, and unbeknownst to them, the tree they are flying toward is the one they just left.” 

Mesure, cofounder of the nonprofit Fatal Light Awareness Program (FLAP), set off behind one of the buildings. “It is a perfect storm here,” he said, “because of the beautiful landscaping and a nearby river and swamp.” He suspected that the back might kill more birds than the front, and it seemed quite possible: Those walls reflected even more vegetation and a largely uninterrupted swath of sky. The looking-glass land appeared idyllic and inviting, a rich habitat. “I can guarantee that this is a much more lethal façade,” Mesure said. “But the birds fall into the bushes and no one sees them.” At many sites, FLAP volunteers discover a cuneiform of tiny white bones in the dirt.

Mesure has been circling buildings in and around Toronto since 1989, saving injured birds and counting the dead. He is credited with launching what became, in the late ’90s, a growing movement in North American cities along migratory flyways to reduce the estimated 100 million to 1 billion bird deaths caused by collisions with windows every year. FLAP, formed in 1993, initially focused on light emanating from buildings at night, which can disorient birds; it now focuses on windows, which kill more birds and at all hours. Because of FLAP’s efforts, Toronto is seen by many in the ornithological community as a model of a city that does right by birds: In 2007, it was the first to produce bird-friendly green-building guidelines; since 2010, developers receive building permits only if design specs consider bird safety; and several older properties have been retrofitted to reduce bird strikes.

Yet Mesure and his collaborators find that despite a 25-year public-awareness campaign, nearly a decade of regulation, and a 2013 court ruling that building owners can be held liable for avian deaths, Toronto and its environs remain a lethal layover. Thousands of birds still die as they traverse the city, following routes etched in their genes millennia ago. Other urban centers and regions where similar grassroots campaigns have led to policy changes—mandatory rules in some, voluntary guidelines in others—are still deadly. The piecemeal efforts cannot outpace a few chronic realities: Millions of older buildings, including homes, have not been retrofitted, and clear or reflective glass remains a construction mainstay.

“It is an exercise in honey versus vinegar.”

FLAP and a coalition of partners are pursuing second-wave approaches, including new types of glass, new building guidelines, and a new app—all of which they hope will ripple out and persuade everyone from architects to building managers to homeowners to take birds into consideration. “It all takes time,” says Mesure. “It is an exercise in honey versus vinegar.”


he waist-high freezer in FLAP’s office was packed this summer with birds collected during the spring migration. Near the top lay a Virginia Rail, the browns and grays of its feathers and the orange of its feet and curved beak still vibrant. Stacked below were Yellow Warblers, Red-winged Blackbirds, Golden-crowned and Ruby-crowned Kinglets, and several dozen other species. During the fall migration, mortality is typically much higher as older birds are joined by multitudes of the newly fledged; FLAP sometimes collects as many as 200 kinglets a day in October. The frozen birds ultimately will be photographed as part of a vast annual still life and stored at the Royal Ontario Museum, becoming data that undergird death-by-window estimates. Last year, FLAP volunteers collected 2,185 dead and 651 injured birds on routine patrols.

Most casualties are passerines—the order of birds that perch, often sing, and make up more than half the roughly 11,000 avian species worldwide. But few birds are safe from windows. In August, FLAP found a dead Double-crested Cormorant, the first they’ve recorded. Although waterbirds and raptors tend to collide with upper-story glass, most birds hit lower levels, when foraging for food next to reflective buildings or trying to fly through transparent atria and walkways.

Marking glass so that it’s visible to birds is the most common way to prevent collisions. Daniel Klem, Jr., an ornithologist at Muhlenberg College in Allentown, Pennsylvania, identified a helpful rule of thumb for such patterns: Birds generally will not fly into a gap less than two inches high and four inches wide. (Recently, a tighter array, two inches by two inches, has been used to deter small species such as hummingbirds.) Stickers or decals are applied in sheets with graph-like regularity or with whimsy. “One of the most interesting developments is the increasing use of art to create these really beautiful solutions, to use glass as a canvas,” says Krista De Groot.

A Canadian Wildlife Service biologist, De Groot has been evaluating small white dots called Feather Friendly markers at the federal Pacific Wildlife Research Centre in Delta, British Columbia. In the two years before the center was retrofitted, she and her colleagues recorded 53 deaths from window strikes; since dots were applied in 2016, only four.

Working on the same principle, patterns can also be etched or printed on glass in various processes. One type, called fritted glass, was installed at Swarthmore College’s science center, in Pennsylvania, in 2004, and researchers there discovered that the new glass was energy-efficient, too. “There is a lot of overlap between being bird friendly and controlling heat and light,” Christine Sheppard, director of the glass-collisions program at the American Bird Conservancy, says. Energy costs and bird deaths have also fallen at the Javits Center in New York City since it was retrofitted with fritted glass four years ago.

Some architects consider birds in their blueprints. The Aqua Tower, designed by Chicago firm Studio Gang, for example, features an undulating façade, breaking up walls of windows with visual noise that alerts birds to their presence. A transparent screen with regular, faint horizontal lines was placed 18 inches in front of the windows on the New York Times building, designed by Renzo Piano and FXFowle, to similar effect. Architects have also used angled or punctuated glass panels, opaque glass, colored screens, or less glass altogether. 

As effective as these approaches are—as well as a suite of other strategies outlined in guides by Toronto’s city-planning office, the American Bird Conservancy, and various Audubon chapters—they can’t get around a simple reality: People overwhelmingly want clear glass, an unobstructed view outside. A glass invisible to people yet apparent to birds has been theoretically possible since the ’70s, when researchers found that certain birds see ultraviolet wavelengths. But researchers say it has been challenging to put UV patterns on the outermost window layer, where they’re most perceptible to birds.

A few years ago, Walker Glass Company of Montreal succeeded, using a UV coating produced by Pilkington. Depending on the light, AviProtek T is transparent to people looking out, faintly apparent as thin lines to people looking in, and, according to field tests by Klem, highly visible to many birds. (Walker is licensing a patent that Klem holds on UV pattern application.) 

The idea of a UV-patterned glass option has been controversial. Some experts, including Sheppard, argue that because of interspecies variability, certain birds will not see the reflected UV signals. And there is some debate about which of two very different testing methods—field versus indoor tunnel—should be used to evaluate success. Even so, support for UV glass is clearly mounting. “All products have a range of effectiveness, and so it is all about what is acceptable to a consumer,” De Groot says. “But the UV really has the promise of a mass uptake.” Architects could get their clear glass towers and homeowners their plate glass windows without sacrificing the lives of birds.  



uildings all over North America have been identified as unintentional avian abattoirs. But because of one particularly lethal location, UV glass, as well as other bird-friendly building products and designs, may be on the cusp of wider adoption in Canada—and perhaps beyond. 

A decade ago, droves of birds were flying into the glass façades of Yonge Corporate Center in Toronto, a well-wooded, well-landscaped site owned by real estate company Cadillac Fairview. In 2010 alone, FLAP volunteers found 826 dead birds there, including two threatened species. FLAP and Klem became central witnesses in a suit brought by the law firm Ecojustice. In 2013 a provincial court judge ruled that the company was liable for the deaths (though it was acquitted because it had, in the meantime, retrofitted its building using dot stickers). “We got a very strong legal precedent: If you are killing birds with windows, you are running afoul of the law,” Albert Koehl, the lead prosecutor, says. “The precedent makes a lot of companies anxious because they know they can be prosecuted.” 

Koehl, Mesure, and others expected the decision would quickly lead to Ontario-wide regulation. But little happened, Koehl says, in part because real estate companies “have huge power, and governments are leery to regulate them.” This spring, Ontario’s Ministry of Environment Conservation and Parks took action. It hired CSA Group—an international company based in Canada that recommends industry codes, which often become the basis for federal law—to fast-track green-building standards for Ontario. CSA Group is expected to release a template for bird-friendly products and designs in early 2019.

CSA Group’s recommendations could change norms in Canada, accomplishing what many activists across North America have long hoped national legislation would. If the voluntary standards are adopted as regulations by municipalities throughout Canada, as some experts expect, birds would be considered from the get-go: Making birds central to design could become routine professional practice—no longer dependent on this architect or that city’s laws, this property manager or that activist. “It has been, in many cases, just the sheer tenacity of individuals,” De Groot says. “They have single-handedly made a huge difference.”

The standards could have a ripple effect as well. Just as the early accomplishments in Toronto have spread throughout Canada and the United States, CSA Group’s recommendations are expected by Klem, Mesure, and others to have international impact. The company works on codes and standards around the world and has nine offices in the United States. The hodgepodge of regulation everywhere is, as Mesure notes, “driving architects crazy.” Bird-friendly elements are required in San Francisco, voluntary in Palo Alto, required in Minnesota, pending in Maryland, required in Toronto, voluntary in Calgary. “As cities find that there is a national standard that has been created, it is going to make them stand up and notice that this is serious,” Steven Morren, of Walker Glass, says. “It is going to make it easy for them.”

Simplicity is also critical for the millions of older buildings and homes that are inadvertent death traps. As he stood near the Markham office building in the shade of pines and cedars, a varied habitat loved by kinglets, Mesure did a rapid, informal assessment on his phone. FLAP is developing a 24-question app that can quickly gauge a building’s “bird threat.” The app, scheduled for release in the next six months, distills the 400-question audit FLAP uses to provide recommendations to building managers. In Mesure’s view, streamlining assessment is key to motivating owners and managers of millions of problematic buildings to do retrofits, which usually doesn’t require treatment on all sides or floors. After three minutes, he had the building’s rating, which matched his own assessment: lethal by day, moderate by night. Fatalities could likely be reduced by treating windows at canopy level alone, on all façades.

The ease of the app could help FLAP and similar organizations reach private homeowners, too. “The residential community is really, really tricky,” Mesure says. Home windows are estimated to cause between 44 and 90 percent of bird-strike deaths, far more than the office buildings and glassy condos that have drawn the most public attention. Trees and feeders bring birds in close to reflections of trees and feeders. Unless homeowners hear a thud or see the powdery traces of impact blurring their view, they often don’t know the risk their residence poses. Guided by the app, homeowners could make their properties safer for birds.

Preventing collisions is one of the few straightforward things a person or company can do to protect birds, which face myriad threats. BirdLife International’s 2018 report found that of the world’s avian species, 3,967, or about 40 percent, are in decline, and 13 percent are vulnerable or endangered. Habitat loss, pollutants, cats, power lines, and climate change all contribute to the losses—to a growing quiet in the ever noisier world. 

Unlike those threats, people regularly encounter the casualties of bird strikes. Most everyone sees the toll windows take at some point, whether it’s the thwackagainst a sliding-glass door or a warbler carcass on the sidewalk outside their office. And, says Mesure, “it is slowly, but surely, becoming socially unacceptable to not deal with this issue.”


This story originally ran in the Fall 2018 issue of Audubon as Safety by Design.” To subscribe to our magazine, please make a donation today.