Authored by Dr. Daniel Klem, world-renowned ornithologist and expert in the area of bird deterrence. Billions of birds are killed each year around the globe due to collisions with  clear and reflective sheet glass as window panes in residential and commercial structures in urban, suburban, and rural landscapes. Within the last decade, however, meaningful progress has been made to save more bird lives from windows by various building industry and avian conservation constituencies.

What we know: The factual evidence

Dead and dying birds due to glass collissions most often are hidden from view in the vegetation planted near human dwellings. Our collective knowledge reveals that clear and reflective windows of all sizes are invisible to all birds. What explains which species in what numbers are killed striking a specific window is the density of individual birds in the immediate vicinity (within 10 meters) of that invisible hazard. Birds succumb to head trauma, and a bird the size of a sparrow need only be perched one meter from a window to build up enough momentum to kill itself striking the glass surface.The annual toll exacted by windows currently is estimated at 16-42 million in Canada, 365-988 million in the United States, uncountable billions worldwide. This specific invisible threat to bird life is adversely affecting our planet’s biodiversity.



Solutions: Designing buildings to prevent unintended collisions

Over the last decade, more media attention has attracted the interest of a growing public and building industry professionals such as glass manufacturers, architects, developers, and landscape designers. This increased awareness and the action it has stimulated is the result of the science explaining the glass threat to bird life and justifying its prevention. North American efforts have developed and guided an ever-increasing number of solutions to protect and save these special creatures.

Just one of numerous helpful practices is to treat sheet glass from grade level to the height of 16 meters. This height is to ensure mature trees will not have their attracting images reflected in widows to deceive birds attempting to reach them. Regionally, Minnesota has passed a bird-safe building law that is statewide in scope in the U.S., and the Ontario Environmental Protection Act (EPA) contains several content provisions relevant to protecting birds from windows in the province. Municipal guidelines that are both voluntary and mandatory bird-safe measures have been enacted in Calgary, Alberta, New York City, Portland, Oregon, San Francisco, California, and Toronto, Ontario. Bird-safe building design and practices to assist architects and other building professionals have been published by the American Bird Conservancy, New York Audubon Society, and City Planning departments in Calgary, Toronto, Portland, and San Francisco.

Whereas as few as ten years ago there were no bird-safe products available to architects, today there are many and their number is growing. Scientific experiments inform us that bird-safe patterning must uniformly cover the glass surface. Elements making up the pattern need to be separated by 10 cm if oriented in vertical columns, and 5 cm if oriented in horizontal rows. The elements can be of any shape such as dots, lines, rectangles, and can be as small as 2 mm covering 7% of the surface offering the same protection as elements 13 mm wide covering 50% of the surface. Elements can be visible to bird and human eyes, and be applied by films for retrofitting, and by acid etching and ceramic frit for remodeling and new construction.

Effective bird-safe patterning invisible to humans but visible to birds are created using ultraviolet (UV) reflection and absorption areas. The use of UV patterning to prevent bird-window strikes is an elegant, and perhaps the best, solution because it protects birds and preserves the human of purpose windows providing an unobstructed view to the outside from a protected indoor space. Whether retrofitting or creating new panes for remodeled or new structures, patterning applied to the outside facing glass surface, what architects refer to as Surface 1, is essential to be effective.



The toll exacted by windows on select species and birds in general is significantly harming their ability to survive. The  invisible deathtraps our windows pose to birds are one that they cannot defend or alter their nature to protect themselves. We humans need to protect these innocent, defenseless, and useful marvels of Nature that play an integral role in the Earth’s diverse ecosystems. We can solve this problem for birds, but not without the creative help of architects and other members of the building industry and those legions of individuals passionately committed to saving more bird lives from glass worldwide.


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