One early May morning a few years ago, I scrambled around Chicago鈥檚 high rises in search of dead birds. Talk about a somber start to the day. Just imagine standing there, looking at a bright, tiny feathered form lying completely still among grey, dispassionate buildings. Now envision witnessing such a sight for days on end during migration season. Who would do that? The nonprofit (CBCM), for one. That May morning, I was out with the organization鈥檚 energetic director, Annette Prince. She and her volunteers troll Chicago鈥檚 most notorious bird-killing buildings during the spring and fall for avian victims, transporting the dead to the Field Museum and the living to a wildlife rehabilitation center. That day, Annette and her crew rescued 17 birds and found 20 deceased. And that鈥檚 just in a portion of one city in one day. Imagine the carnage during a season.
Why are these birds dying? You might be tempted to say 鈥渓ights.鈥 Well, that鈥檚 only a part of the answer. Sure, birds can be tricked by building illumination, thinking it's a navigational cue like the stars or moon. But typically birds don鈥檛 just crash into those lit facades to rain on the ground below. Rather, pulled of course, they likely settle into the city to rest, where they risk flying into a window (say, in a lobby) when they take off again. 鈥淚t鈥檚 not, in my view, beacons that are attracting these animals to their deaths on the tops of the buildings,鈥 said Daniel Klem, an ornithologist at the Acopian Center for Ornithology, in an I wrote after my trip, 鈥淚t鈥檚 a secondary effect that gets them, and that鈥檚 the glass on the ground.鈥
Building strike fatalities. Photo by Joanna Eckles/Minnesota 探花精选
The thing is, birds don鈥檛 see windows as a barrier. That鈥檚 one of the reasons that glass is the second-largest manmande threat to birds after habitat loss. Klem estimates that at least a billion birds鈥攔oughly five percent of the bird population after breeding season鈥攄ie annually across the United States by colliding with windows.
And this isn鈥檛 just happening in cities. It could be going on in your neighbhorhood, in your own backyard, out of sight, any time of year. To read one man鈥檚 grisly tail of what happened to a feathery visitor after it conked itself out on his window, click .
So what can you do to outfit your house with crash deterrents? The list below came from a paper by Daniel Klem, which he presented last year at a Partners in Flight conference.
1) Cover windows with netting.
2) Move bird feeders, watering areas, perches, and other attractants to within one meter or less of the glass surface.
3) Place decals on or hang strings of objects in front of windows such that they uniformly cover the surface and are separated by 10 cm (4 in) or less in vertical columns or 5 cm (2 in) or less in horizontal rows. (*Author鈥檚 note: In other words, one lonely decal isn鈥檛 enough of a warning sign. The idea is to produce a visual disturbance that signifies to birds, 鈥淪top!鈥)
4) Use one-way films that consist of patterns and color shades acceptable to homeowner and commercial building manager; these films provide a minimally obstructed view from inside while rendering a window opaque or translucent when viewed from the outside.
5) Reduce the proportion of glass to other building materials in new construction.
6) Use ceramic frit glass with 0.32-cm diameter translucent appearing dots separated 0.32 cm apart in new or remodeling existing structures.
7) Angle windows 20 to 40 degrees from vertical in new or remodeled construction.
And what about building managers? There are various solutions, such as installing netting over lobby windows, like after a regular spates of avian fatalities. Last summer, 探花精选 Minnesota revised a set of bird-friendly guidelines that New York City 探花精选had published, with expert input, in 2007. See for links to those resources. And see if your city participates in campaigns.
Stay tuned next week for more on bird collisions.
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