Climate Impact November 8, 2023

Glass buildings are threatening the world’s most beautiful birds. These design moves can save them.

The haunting thud of a bird striking glass is a sound we all know. It’s so common, in fact, that building collisions claim the lives of up to one billion birds each year in the U.S. alone.

“The whole push for bird-friendly glass doesn't have to be some kind of trade-off, where birds win and architecture loses. Instead, it's a chance to embrace a new design perspective. The ultimate goal is to reach a stage where bird-friendly design is just design.”
Carl Giometti, project architect

Birds are more than just beautiful creatures. They’re pollinators, pest controllers, and ecosystem stewards. They play countless roles in keeping our natural environment healthy. But the sad truth is that their numbers are dwindling. According to the State of the World’s Birds report, nearly half of all bird species worldwide are declining, and one in eight are threatened with extinction. While much of this reduction is due to habitat loss from climate change and human encroachment, as well as predation from invasive species, the built environment is also largely to blame—chiefly large expanses of glass, though other factors come into play.

Part of the problem is that birds don’t recognize glass the way we do. Where we see reflections of the sky and surroundings, they see extensions of their world—often with deadly results. Luckily, awareness of how certain design decisions affect the way birds see buildings is growing and progress is inching forward. Cities like Washington, D.C., San Francisco, and New York have adopted bird-friendly building standards, though federal legislation is trailing behind. There’s still a long way to go, but these cities show that such policies are not only possible, they’re also effective at preventing bird-window collisions. With a bit of urgency and goodwill, we could save millions of birds just by changing a few aspects of how we design our buildings and landscapes.

Here are the stories of two projects that are raising the bar on bird-friendly design:

Florida International University, Tamiami Hall and College of Engineering & Computing Center
Miami, Florida

With hundreds of glassy towers and a prime location along Florida’s coastline, where many birds funnel southward, Miami makes an ideal laboratory for testing bird-friendly design solutions. To that point, Florida International University (FIU), a champion of environmental progress, has been working toward mitigating bird fatalities caused by building collisions.

Birds in search of a safe place to rest or refuel often mistake reflections of treetops in windows for real perches. The first step in solving this problem is to make glass less transparent or mirror-like. At Tamiami Hall—a new student residence on FIU’s campus—the design team collaborated closely with the university’s department of architecture to implement a simple, yet astonishingly effective technique known as “fritting.” The process involves baking patterned ceramic paint onto the surface of the glass, creating visual cues that alert birds to the presence of a barrier, especially at tree-level and below where collisions are more common. This is in line with the American Bird Conservancy (ABC)’s “first 100 feet above grade” rule. Each floor of Tamiami Hall is also designed so that no room has glass on both sides, preventing birds from attempting to fly through the building. And what’s more, all treated glass reduces glare and cooling expenses by minimizing solar heat gain and visible light transmission.

"We're taking these bold steps to tackle both the bird-friendly issue and light pollution."
Dr. Gray Read, associate professor at FIU's School of Architecture

But glass alone isn’t solely to blame. Artificial light at night—both indoors and outside—disorients and confuses birds, exacerbating the problem. When brightly lit buildings and upward-facing landscape lights project into birds’ migratory airspace, they can disrupt their navigation, causing them to deviate from their normal flight paths, often directly into buildings. Excessive outdoor lighting also creates light pollution, which the astronomy department has been wanting to address for their own purposes. To combat these challenges, FIU has implemented a ‘lights out’ policy after dark, redirected outdoor lighting downward, and transitioned to a softer red spectrum. Dr. Gray Read, an associate professor at FIU’s school of architecture, adds, “We’re taking these bold steps to tackle both the bird-friendly issue and light pollution.”

FIU President Ken A. Jessel has been a supporter of bird-friendly design from the get-go. All new construction on campus—including the soon-to-be College of Engineering & Computing Center—adheres to contract-mandated standards, such as the use of fritted glass, enforcement of a ‘lights out’ policy, and controlled inside and outdoor lighting. Dr. Read underscores that embracing bird-friendly design reflects the community’s commitment to ethical design and fosters a more harmonious campus environment.

University of Minnesota Bell Museum
St. Paul, Minnesota

At the University of Minnesota’s Twin Cities campus, the Bell Museum takes visitors on a journey through the state’s natural history, exploring the intersections of art, science, and nature. With a collection of over 45,000 bird specimens, some showcased in fantastical dioramas, the Bell inspires a connection between environmental experiences of the past (within its walls) and the immediate present just outside, informing our collective future.

Situated along the Mississippi River, the U of M is home to a plethora of bird species that migrate northward in the spring. “It’s not just about bird-friendly design strategies being an option for nature and science-centered institutions; we all must consider the impact of our buildings on biodiversity,” says Dr. Holly Menninger, the museum’s interim director.

The Bell’s design plays a crucial role in supporting its natural history narrative. The building features sustainably sourced materials from local suppliers, including granite, panelized steel cladding inspired by the state’s mining heritage, and Forest Stewardship Council-certified thermally modified white pine siding. Less than 30 percent of the museum is comprised of glass, and all the exterior glazing uses a bird-friendly pattern. 

The project’s success hinged on finding the right frit patterns, spacing, colors, and low reflectivity glass types. Two custom designs were used: one with closely spaced dots in select locations and the other with thinly spaced horizontal lines.

“As architects, we're not just designing places for people to thrive; we're also building homes for other creatures. It’s an ethical challenge—we’re trying to connect with nature through glass, yet we’re inadvertently killing the wildlife we’re trying to admire.”
Doug Pierce, project architect

The dotted design, covering 40% of the glass area on the south, east, and west facades, serves a dual purpose. It deters birds in areas where human views of the outdoors aren’t crucial and reduces solar heat gain, thereby cutting energy usage and operational carbon emissions. Most of the glazing, however, uses a special bird-friendly pattern that the project team designed with the help of Owatonna-based fabricator Viracon and Audubon Minnesota. It features thin, high-contrast, medium-dark gray horizontal lines with 1-inch spacing. This glass treatment was applied to all facades where human views of the outdoors were a priority, as it not only effectively deters birds but is also visually appealing to visitors.

Tunnel tests are commonly done to gauge glass effectiveness against bird strikes by releasing them into a tunnel with clear and patterned glass openings. Their behavior is measured via the threat factor—the percentage of birds flying toward clear glass. Factors under 30 are considered effective, and lower scores are even better. The Bell’s glass scored below 15. Equally important was pattern spacing, with tests showing that birds tend to avoid patterns that are spaced less than two inches in height and four inches in width.

A lot of thought and intention went into the project’s bird-friendly design, stemming from local partnerships. For example, the Bell is involved in Project BirdSafe, an Audubon Minnesota initiative with the goal of reducing hazards to birds. The program’s volunteers have made significant strides in advancing our understanding of bird fatalities caused by glass collisions. “What materialized is a true reflection of who we are, our values, and how we show up in our community,” Dr. Menninger says. However, to obtain comprehensive data on where, when, and how birds are dying, wildlife conservationists are stressing the importance of backing from government agencies, NGOs, and professional scientists.

Green building practices have long prioritized energy efficiency, sustainable materials, and resource conservation. But what about the impact of buildings on birds and other wildlife? After all, a structure can’t claim to be truly environmentally friendly if it’s not kind to its surrounding ecology. While there’s no one-size-fits-all solution to guarantee the safety of all birds, a combination of design moves—like using fritted or opaque glass, reducing the amount of glass used on buildings, and controlling indoor and outdoor lighting—can lead to greater harmony between the built and natural environments.