As many as 1 billion birds suffer head trauma and die from flying into buildings each year, leading Audubon North Carolina to team up with the U.S. Green Building Council in a statewide initiative to minimize threats to birds in the built environment.
Kim Brand, project coordinator of Audubon North Carolina’s new Bird-Friendly Communities initiative, detailed building characteristics that create problems for birds and offered solutions for architects to consider during a Nov. 18 lunch and learn hosted by the Cape Fear Provisional Branch of the U.S. Green Building Council’s North Carolina chapter.
Architects attending the event earned American Institute of Architects (AIA) continuing education credits through the American Bird Conservancy, and learned about a Leadership in Energy and Environmental Design (LEED) credit awarded for buildings that deter bird collisions.
The greatest hazard in built environments is glass, Brand explained. Birds are unable to discern unbroken expanses of clear glass and other glazed surfaces on buildings as obstacles.
“They don’t perceive glass as solid. They can’t respond to architectural cues like we can,” Brand said.
Reflections of vegetation and the sky mislead many birds to interpret glass surfaces as familiar habitat, but even if the glass is transparent, birds will often attempt to access possible perches or indoor plants they see on the other side — if they are looking straight ahead, which Brand said rarely happens.
“Birds do see the world differently than we do,” Brand said. “It’s much more important if you know whether there are hawks above you that might swoop down and grab you up in their talons than it is to see what’s directly in front of you.”
Architects must limit the amount and type of glass on the first three floors of a building, considered the most dangerous area for birds, to earn the LEED credit for bird-safe design. Only 15 percent of all glazed surfaces on the bottom floors can be clear glass; texture, color or opacity must be added to the remaining glass to reduce threats from transparency or reflections.
Wilmington architects Chip Hemingway and Daniel Hill, of Bowman Murray Hemingway Architects, spent more than a year reviewing the formula for the LEED credit eligibility for nine renovated buildings and three new buildings at Audubon North Carolina’s Pine Island Sanctuary and Reserve.
Features like mullioned glass windows and exterior window screens were selected to divert birds from windows. Hemingway said his new understanding of bird-friendly design principles will likely inform future projects.
“It’s another facet of bringing buildings into harmony with the surroundings,” Hemingway said.
Etched, fritted or patterned glass are other options, in addition to colored fiberglass and glass blocking. Window stripes, 2 inches apart if horizontal and 4 inches apart if vertical, are a strong deterrent for birds, but often considered visually distracting for people.
Glass treatment must be applied to the exterior to be effective, Brand said.
Protective screens and shutters also deter birds by minimizing a bird’s exposure to transparent or reflective glass.
Because birds are believed to see more of the ultraviolet spectrum than people, an innovative but expensive glass invented by European-based manufacturer Arnold Glas inscribes a UV-reflective pattern on windows that is barely visible to humans, but sends a strong signal to birds.
Architect Eric Jabaley of Dogwood Design Studio said more affordable solutions from window manufacturers are needed to make bird-friendly designs appealing. He said most of his clients request as many windows as possible and set strict project budgets.
“That is the ideal solution, but we’re just not there,” Brand confirmed.
Guidelines for the LEED credit also limit the light a building projects, especially at night.
For birds migrating at night, artificial light poses another problem, especially in foggy conditions. The birds use the moon and stars as navigational cues, Brand said, but become confused by strong beams of light shining from below.
“Light coming from below is completely novel to them. Nothing in their evolutionary history really prepares them for that,” Brand said.
Millions of birds from hundreds of species, including black-throated warblers and wood thrushes, pass through North Carolina each spring and fall when traveling along the Atlantic Flyway migration route.
The majority of crashes occur when birds migrate, Brand said, so familiar species like robins, mockingbirds and sparrows are less likely to sustain injuries from flying into buildings.