Glass - silent but deadly How about bringing the issue a bit closer to home, you say. Sure, we know about the problem of night-migrating birds hitting lit towers and of course we're concerned. But what about the birds that hit the picture window in our living room or the patio doors at Aunt Mae's cottage or the shiny glass walls of the university building down the road? Okay, so we've only seen the evidence once or twice but we've heard that sickening thud a few times and the neighbourhood is teeming with cats... If you believe that windows in general pose a serious threat to birds, you're perfectly right. Daniel Klem Jr., a biologist at Muhlenberg College in Pennsylvania, conservatively estimates that every year over 100 million birds die as a result of hitting glass in the United States alone. Dan's studies show that glass in any form - large windows or small, in tall buildings or modest homes, even a car windshield - is a potential killer. Tinted or clear, glass is invisible to birds. If it reflects their natural habitat, the trees, shrubs or sky where they would normally take refuge from perceived dangers, chances are good they'll fly towards it. Their behaviour may be further influenced by other factors: the proximity of a tree to the window, the angle at which the bird sees the reflection, the positioning of a feeder. Another problem situation, one which FLAP members encounter often, is where a large leafy plant is placed inside a building and birds can see it clearly, but not the intervening glass wall. If they are in an alien environment (such as Toronto's downtown core) where a person walking by will frighten them, they're sure to head for that leafy plant. A panicked bird will smack into a window with greater force and often disastrous results. The same holds true in places where glass on both sides of a building creates the illusion of an unobstructed corridor. Birds will gather momentum as they prepare to sail through the perceived passageway. Not all birds are killed outright. (Dan found one of every two strikes to be fatal.) The survivors may be merely stunned, but if predatory animals (cats, dogs, hawks, raccoons, even squirrels) have learned to patrol the area for casualties, we may never see the fallen birds. Hence, the general perception that window kills are a rare occurrence. But Dan Klem, who has monitored various types of buildings in different settings, and conducted field and laboratory experiments to better understand the problem, believes that the much-publicized loss of birds to cats, oil spills and pesticide poisonings accounts for considerably fewer deaths than windows and glass walls. Seemingly innocuous structures such as houses take a considerable toll in birds. Add to that the fact that more and more buildings are constructed using reflective materials and you see why this becomes a serious concern. FLAP members Michael Mesure and Edmée Steiner have been monitoring one reflective building in North York. Most of the walls are a deep, shiny blue-green giving a perfect reflection of the woods immediately to the north and east of the structure. Songbirds were hitting the building and falling into ventilation shafts covered by grates. Anyone looking down could see feathers, skeletons and decompos-ing bodies, apparently from birds that fell in and couldn't get out. Alerted to the problem, building management called in an expert. Aldrick Waterman, who trains hawks to keep Toronto's airport runways free of birds that may collide with airplanes, devised an ingenious system. Cables were extended from the roof of the six-storey building to trees on the hillside some 20 yards away. Three "hawks" with their wings tucked back to simulate a dive, were attached by their wing tips to the cables so that the silhouettes would sway ever so slightly with the wind. Mike and Edmée have noticed a substantial decrease in the number of birds crashing into the north wall of this building since the system was introduced. (On the other sides of the building, which remain silhouette-free for a variety of reasons, a few birds are still hitting.) This is one way of dealing with an existing problem at a commercial building. (See insert for suggestions on what you as a homeowner or apartment dweller can do to reduce avian mortality.) In the next issue of Touching Down we will focus on architectural designs that take birds into account, so that window kills are minimized or eliminated.