Design Choices Protect Birds from Building Collisions
Second only to habitat loss, collision with windows poses the largest human hazard to birds, according to Daniel Klem Jr., a biology professor at Pennsylvania’s Muhlenberg College and the world’s foremost expert on the phenomenon of birds flying into buildings. These collisions kill more birds than hunting, cat predation, and pesticide exposure, he says. Klem’s research suggests that between 100 million and one billion birds—one to ten birds per building—die each year in the U.S. after striking windows.
Birds often fly into clear glass when they see through it to vegetation, the sky, or even the skyline on the other side of the building. Birds also fly into reflective glass, apparently unable to discern the reflections of trees and clouds from the real things.
Fortunately, modifications to building designs can reduce bird collisions. The most effective change is eliminating mirrored glass. Using architectural details to break up mirrored glass visually can also help birds understand that it’s a solid surface. Tilting mirrored glass so it reflects the ground can encourage birds to steer clear. The incorporation of an etched pattern, a ceramic frit, or photovoltaic panels into a glass curtainwall may also make it visible to birds, especially if the glass is also nonreflective. Birds sometimes fly through spaces as small as a human handprint, however, so patterns have to be tight to be effective.
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Lightshelves, shutters, and other shading devices make it easier for birds to recognize a façade as a solid surface. Fox & Fowle Architects and the Renzo Piano Building Workshop, for example, selected a screen of horizontal ceramic cylinders for the New York Times headquarters in New York City, due to be completed in 2007, for its bird-friendliness in addition to its aesthetic and shading properties.
For problematic existing buildings, some retrofits can mitigate the problem. Nonreflective window film—the kind commonly used for advertising on bus windows—is an inexpensive, effective way of bird-proofing glass. The Fatal Light Awareness Program (FLAP), a Toronto, Ontario, nonprofit devoted to preventing bird-building collisions, recommends Scotchprint, produced by 3M, and CollidEscape, produced by Large Format Digital. The Earth Rangers Centre in Woodbridge, Ontario, for example, features 3M window film in a decorative tree pattern that warns birds of the solid surface. Other sources of pattern or visual noise include traditional window screens, blinds, artwork on the glass itself, and—in extreme situations—netting.
Most experts are pinning their hope on the development of a special glass with an embedded or applied UV pattern. Ornithologists believe that such a pattern, though invisible to humans, would be apparent to birds, enabling them to see the glass as a solid surface. “If that works, we’ve got it made,” says Michael Mesure, executive director of FLAP. Until this UV glass is widely available, however, architects, designers, and building owners should be aware of their ability to protect birds through other design and retrofit choices.
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