One early May morning a few years ago, I scrambled around Chicago’s 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 Chicago Bird Collision Monitors (CBCM), for one. That May morning, I was out with the organization’s energetic director, Annette Prince. She and her volunteers troll Chicago’s 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’s 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 “lights.” Well, that’s 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’t 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. “It’s not, in my view, beacons that are attracting these animals to their deaths on the tops of the buildings,” said Daniel Klem, an ornithologist at the Acopian Center for Ornithology, in an article I wrote after my trip, “It’s a secondary effect that gets them, and that’s the glass on the ground.”
The thing is, birds don’t see windows as a barrier. That’s 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—roughly five percent of the bird population after breeding season—die annually across the United States by colliding with windows.
And this isn’t 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’s grisly tail of what happened to a feathery visitor after it conked itself out on his window, click here.
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’s note: In other words, one lonely decal isn’t enough of a warning sign. The idea is to produce a visual disturbance that signifies to birds, “Stop!”)
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 Chicago’s FBI building did after a regular spates of avian fatalities. Last summer, Audubon Minnesota revised a set of bird-friendly guidelines that New York City Audubonhad published, with expert input, in 2007. See this post for links to those resources. And see if your city participates in Lights Out campaigns.
Stay tuned next week for more on bird collisions.
"Law and Order: Special Avian Victims Unit (Or, the Trouble With Windows)" (September, 2010): Last September, several groups prosecute a Tronont-based building complex for emitting a harmful contaminant that affects birds.
"Pain in the Glass" (November, 2008): Each migration season, millions of birds die in cities by crashing into buildings. Now a growing trend toward sustainable design could open the door to safer passage.
"Clear and Present Danger" (March, 2004): Millions of birds perish every year from crashing into glass windows. After decades of inattention, biologists, builders, and architects are joining together on solutions that will benefit both people and the birds.