Windows: an unintended fatal hazard for birds
We at SBTH are frequently asked what to do about window kills. Following is an article written for us by Dr. Daniel Klem, Jr., who is the acknowledged expert in the subject.
Habitat destruction is our greatest assault on wildlife because when we markedly alter or eliminate a habitat we also eliminate the fundamental resources upon which life depends; life cannot endure without food, shelter, or water. Certainly windows kill far more birds than wind turbines, power lines, pesticides, and domestic cats. Yet, it is fair to claim that this horrific loss of birdlife from collisions with windows is largely ignored by most, most regrettably by those that can do the most to prevent it: members of our conservation community whose mission is to protect life, and the building industry whose mission it is to construct human structures, increasingly with modern designs that are lavishly covered with glass.
Why is the glass threat to birds largely ignored? After studying bird-glass collisions for over 34 years, my view is that the attractive and utilitarian value of windows for humans is so great – economically, psychologically, and aesthetically – that we cannot imagine such a valuable product doing harm, or even considering altering these useful product in any way that would inhibit the meaningful benefits they offer. I have never advocated eliminating windows in any human structures, but I have recommended covering or altering panes by those willing make a small change in the way they see through their windows in order to protect birds. And ideally I have tried to investigate how new types of glass can be manufactured such that we humans see through windows the way we do now, but birds viewing the same windows from the outside see patterns in the panes that alert them to danger.
Covering windows with conventional insect screening is an effective lifesaver because it keeps a flying bird from striking the unyielding surface. Many homeowners have built their own safety nets, and a commercial source (see www.birdscreen.com) has existed to purchase residential home screening for some time now. Covering reflective windows on the outside surface with patterns, such that the elements making up the pattern are 2 to 4 inches apart transforms these panes into barriers that birds avoid. If the pattern is oriented vertically like blinds the elements making up the columns can be as much as 4 inches apart, but if oriented horizontally in rows the elements need to be 2 inches apart. The actual elements of the overall pattern can be any opaque or translucent object: circles, diamonds, stripes, hawk silhouettes, spider webs, or ultraviolet (UV)-reflecting maple leaves. My experiments reveal that if you cover an offending window with patterns composed of elements with this density, you eliminate bird strikes altogether. Applying patterns with greater spacing between elements, one or more, you reduce but do not eliminate fatal strikes. The more elements the greater protection and lives saved, fewer elements the greater risk and more lives lost.
My most recent experiments have produced some hopeful results for using UV patterns to alert birds to the dangers of windows. But whether UV signals, or some other inventive techniques, are actually effective in making glass and plastic safe for birds manufacturers must be convinced that there is a market for such products. It is therefore imperative that we work together to educate our friends in conservation and those in the building industry that saving birds from this unintended lethal hazard is a practical, ethical, and moral commitment we must make to one of nature’s most useful and exquisite creations. I know no one purposefully seeks to kill birds at the windows of their homes or workplaces. There are international treaties that forbid the intended killing of even a single individual bird, yet so complicated and pervasive is the glass threat that it is only recently that federal agencies have begun to acknowledge the need to address the toll that glass is exacting on protected birds.
The U.S. Green Building Council has created an evaluation system called Leadership in Energy and Environmental Design (LEED) to encourage the construction of environmentally responsible structures, so-called “green buildings.” But none of these sanctioned and award-winning structures are green to me if birds are killed striking the energy saving windows, bathing interiors with natural light, that in turn frequently nurture internal plantings that lure nearby birds to a crashing death from an invisible obstacle. Those charged with creating new versions of the LEED evaluation system need to be educated and encouraged to include a process for designing bird-safe glass and surrounding landscape architecture. To this end, the New York City Audubon Society (www.nycaudubon.org) and the City of Toronto (www.flap.org) have recently published bird safe building guidelines. These recommendations such as those in Chicago (www.birdsandbuildings.org) are fundamental to educating our architects so that their creative designs will be safe and ensure survival of birds, among them the common as well as the rare, threatened, and endangered species. Winning the hearts and minds of architects to this worthy cause of stopping the unintentional killing of birds is essential if glass manufacturers are to judge there is a market worthy of their investment in creating bird-safe glass. No one wants this unintended killing to continue. Surely this extravagant source of bird mortality must be curbed or stopped completely if our future generations are too appreciate, use, and enjoy these magnificent life forms before their diversity and numbers become to rare to see.
Source of more detail: Windows: an unintended fatal hazard for birds. In Connecticut State of the Birds 2007. Connecticut Audubon Society, Fairfield, CT, pp. 7-12 (available at www.ctaudubon.org).
Daniel Klem, Jr., Acopian Center for Ornithology, Department of Biology, Muhlenberg College, Allentown, PA 18104-5586; email: klem@muhlenberg.edu
To read more of Dr. Klem's research, view this article.