Sunday, January 27, 2008

Clear and Present Danger

It was just a sparrow. Just one. I found its dead body on the sidewalk in front of the gym where I try to coax intransigent inches from my aging waistline. Lying on its back in front of the big, plate glass windows, the cause of death was obvious. I made a mental note to collect the tiny body on my way out, so it could permanently repose in a more dignified location. When I picked up the carcass, I instinctively felt the breast of the bird. This individual was very fit, with a well padded chest. The tiny Dark-eyed Junco, a member of the sparrow family, now lies permanently in my garden.

Up at the cabin, another pile of junco feathers lay scattered across the welcome mat at the front door. A small smudge on the adjacent glass window gave witness to the bird’s final moments. In this case, however, the avian victim may have only been stunned by the window. As it lay wounded on the ground, death may have come at the paws of the feral cats that overrun our small neighborhood in the ponderosa pine forest.

Windows! You gotta love the view, especially in our enchanted Jemez Mountains. However, our panoramic view of the world is a veritable death trap for birds. Daniel Klem is a professor at Muhlenberg College in Allentown, PA, and the acknowledged expert in avian window kills. Klem estimates that between 100 million and 1 billion birds die in glass collisions each year in North America. And, this is a conservative estimate based on an average of one bird a year slamming into each of the approximate 100 million homes, apartment building, office towers, schools and storefronts that cover the American landscape. Klem states that glass is one of the world’s greatest bird killers, rivaled only by habitat destruction and perhaps cats. Depending on the number selected among the wide range of estimates, bird kills due to window collisions represent 0.5% to 5% of the 20 billion birds estimated as the North American total population after the breeding season each year.

It is the reflective property of glass that creates the illusion of sky and vegetation that spells doom for birds. Extensive tests conducted by Klem reveal that birds simply do not recognize glass as a barrier. Mortality studies of window killed birds show that the hazard is indiscriminate, meaning that all birds are at equal risk. Window kills affect common and rare birds, large and small species, occur day or night throughout the year, and under most weather conditions. An Indigo Bunting (which is present in the Jemez Mountains) banded after surviving a window collision in Canada, killed itself striking the same window a year later, direct evidence that individual birds use the same migratory path each year.

As ominous as these numbers might seem, they may indeed be quite conservative. Klem’s studies also have shown that of all bird collisions with windows, approximately 50% directly result in death. For the other 50% of birds that lie stunned beneath the window, death by predation is a substantial threat. The household cat, and other predators have learned to patrol the borders of homes and office buildings in search of injured birds.

One emotion unique to humans is the guilt and anxiety we feel upon discovering that the windows of our homes and work places are killing birds. Personally, it affected my decision when replacing all the doors and windows in my home. Wallet opened wide, all glass here now sports multiple panes with faux wood or metal strips. I haven’t found a single bird body in the two years since they were installed.

The best time to make a decision about bird-friendly glass is when the house is designed. There are a number of options available to the builder such as fritted or patterned glass or visual markers that separate smaller panes. Perhaps the most simple and effective treatment is to angle glass 20%, thereby reflecting the ground rather than the sky. Some cities, notably Toronto, have enacted bird-friendly development guidelines for future construction, particularly those that seek “green” certification for their buildings. The Toronto document can be found online .

So, what can you, the homeowner with windows already in place, do to reduce unnecessary deaths at your home? There are a number of online resources although be wary of sites that are actively trying to sell to you. I found the most extensive information at Fatal Light Awareness Program (FLAP), including the Top 10 Ways to Make Glass Less of a Hazard for Birds. g with windows. When a window at the front and back of your home face each other or when two windows meet at a corner they give the impression of a clear passage.

And, finally, although not endorsed by FLAP, there is some evidence that dirty windows are more effective than clean at reducing strikes. So, for those of you looking for the perfect excuse, you never need to wash those windows again!

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