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Clear and Present Danger

Most of the focus on glass is about increasing energy efficiency, but more reflective glazing poses a greater threat to bird species.

September 1, 2010

By Marcia T. Fowle

People who live in glass houses know the sickening thud of a bird striking the glass. Scientists tell us that wherever birds and glass exist, birds are at risk and that most birds do not survive a collision.

Clear and Present Danger
Illustration by Patrick George
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Glazing in buildings of all types—especially those in urban settings—can be a substantial menace to birds. Ironically, energy-efficient glass is an even greater danger to birds than ordinary glass because it is more reflective. With the advent of sustainable-building standards, advanced technology, and market demands, this material is being used more and more.

Birds do not see clear glass as an obstruction; they presumably see open space or reflections of the surrounding environment—sky and vegetation. Each year 100 million to a billion birds in North America are killed indiscriminately by hitting glass.

Members of New York City Audubon became alarmed to discover dead songbirds at the base of certain buildings. Over the course of 11 years, 5,400 victims of more than 104 species from just a handful of Manhattan buildings have been collected by Audubon volunteers. Around the base of one low-rise building they found over 900 birds—mainly migratory species.

Four major cities, Toronto, Chicago, San Francisco, and New York City—all positioned on migration routes—are proactively tackling the issue. The Toronto City Council mandates bird-friendliness in its Toronto Green Standard for sustainable develop?ment. Chicago’s Departments of Environment and of Planning and Development promote bird-safe buildings in their “Design Guide for New Construction and Renovation.” San Fran??cisco is currently considering bird-friendly building codes. And to shepherd the way in New York City, New York City Audubon published “The Bird-Safe Building Guidelines.”

Following the recent inclusion of bird safety in the U.S. Green Building Council’s LEED Reference Guide, similar language is being drafted to shape LEED Innovation credit criteria.

Bird-killing buildings can sometimes be retrofitted. In some, netting is stretched and hung in front of transparent and reflective windows so that birds hit the netting and fly off unharmed. This technique was employed at the former World Trade Center on the lower floors of a particularly deadly facade. More recently, netting was installed on the large viewing window at LEED-certified Jamaica Bay Wildlife Refuge Visitors Center at Gateway National Recreation Area in New York City. At other buildings, special film has been applied to the glass to reduce transparency and reflectivity.

New construction can be bird-friendly. Research has shown that employing a glass product that has been modified with etched patterns or films deters birds. In Germany, Arnold Glas produces a new “bird protection glass,” with a special ultraviolet coating that is visible to birds and almost invisible to humans.

The use of glass to save energy and augment views, daylight, and natural ventilation has become both a “green” design concern and a wildlife concern. With the development of glass that both deters birds and is energy-efficient, sustainable buildings and preservation of wild bird populations will go hand in hand.

Marcia T. Fowle is a member of the Board of Directors of New York City Audubon and co-editor of its newsletter. She is former executive director and president of New York City Audubon, co-author of “The New York City Audubon Society Guide to Finding Birds in the Metropolitan Area,” and former president of the Bird-Safe Glass Foundation.

This article appeared in the September 2010 print issue of GreenSource Magazine.

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