With only five carcasses by New Year’s Day, I thought that we had escaped this year’s killing season at the University of Utah. Then came the dreaded “bird down” message on the first day of classes. We found 10 dead and two stunned cedar waxwings under the windows of two adjacent buildings on the U campus.
Cedar waxwings are a winter favorite here. With their sleek brown coats, black masks, perky crests and flashy yellow and red accents, they look ready for a masquerade party. In the most brutal parts of winter, they survive on fruit. Increasingly, humans construct buildings with lots of glass windows and plant fruiting trees outside those windows. This combination creates hotspots for death.
Cedar waxwings and other birds do not see clear or mirrored windows as hard surfaces. Instead, they see reflections of sky or trees and fly toward them at up to 25 mph. As one of my students asked, “How would we like it if birds erected invisible deadly barriers across our freeways?”
Our research over the past three years has found that planting pear trees within 16 feet of buildings increases the odds of luring birds to their death by 800%. Mirrored windows, instead of clear ones, increase the odds of collisions by 500%.
The death zone outside my building is not an exception. Research published in Science shows North America has lost 29% of its bird population numbers since 1970. U.S. estimates are that up to a billion birds per year die from flying into windows. Fall and spring migrations are often deadly. Our published results provide a rare documentation of a winter death hotspot. In other words, windows kill birds in all seasons.
There are many complicated threats to birds, symbolizing the threats to the biosphere that supports our families and communities. Compared to the other causes of bird deaths — climate change, habitat loss, outdoor cats — the window problem is easier to solve.
You can follow how my students and I are tracking the bird deaths on our campus on our iNaturalist site — University of Utah Bird Window Collision Project. Student support of the Sustainable Campus Initiative Fund allowed us to affix small dots to the outside of the deadliest section of the mirrored windows on the Alfred Emery Building. We found unprotected windows had the same number of window collisions across two years but the protected windows had a 71% reduction in collisions.
We have a small grant from Great Salt Lake Audubon and are seeking more funding to complete window protection for parts of Alfred Emery and James Talmage buildings, the buildings that cause the most bird deaths on our campus.
The less expensive and more energy-efficient solution over the long term is to change building practices. Salt Lake City can join Minnesota and other places by adopting bird-friendly window and building standards for new construction. Details of these standards and solutions for homeowners with collision-prone windows are on the American Bird Conservancy web site. By requiring windows to have tiny embedded frits or ultraviolet patterns, the windows become visible to birds and let the humans enjoy their view.
After documenting so many dead birds, I no longer consider the reflections of mountains or trees from all our mirrored or clear glass buildings to be beautiful. From building plans for the Utah inland port to the new convention hotel and future campus buildings, we should avoid bird-killing designs.
On campus, both the Law School’s ultraviolet patterned windows and Gardner Commons’ fritted windows had many fewer bird deaths than my office building; fritted windows also save energy. All new construction should follow their examples and let the cedar waxwings, and all other birds, live to party on.
Barbara Brown is an environmental psychologist with the Department of Family and Consumer Studies in the College of Social and Behavioral Science at the University of Utah.