People in glass houses should deter bird collisions
From their soaring vantage point, North American birds look down on dwindling habitat and clowders of hungry cats. But they can’t see one of the greatest threats to their survival.
As many as 1 billion birds die each year from collisions with glass windows and doors. A landmark 2014 study conducted by the
American Bird Conservancy found building-glass collisions rated second among humancaused sources of bird mortality. No. 1 was no surprise: An estimated 3 billion birds per year are killed by feral and free-ranging pet cats.
Broken windows and the uncomfortable cleanup of feathery clumps are slowly driving a new industry for bird-avoidance adhesives and new glass products.
Much of the research is occurring in Pittsburgh and the surrounding region.
“Usually with glass collisions, it’s blunt force trauma where they are killed immediately from the concussive aspect, break a neck or rupture something else,” said Jim Bonner, executive director of the Audubon Society of Western Pennsylvania. “Or they’re stunned and may not die directly but are killed falling to the ground.”
Birds that survive the fall are often incapacitated by shock or have broken beaks, wings or legs, providing some predator an easy lunch.
“There are as many reasons why it happens as there are windows,” Mr. Bonner said. “Sometimes in spring and fall you have trauma during night migrations when birds get confused by lights.
In the day they don’t recognize reflections from the world around them, or they’re focused on something and simply try to fly through what looks to be an open empty space.”
Some species are more susceptible to glass collisions. Songbirds at backyard feeders may be so frightened by an impending threat they fly straight into a window. Avian predators diving at more than 100 mph may be speeding too fast to vector away from a fatal glass collision. In cities, resident street-smart pigeons, doves and sparrows crash less often.
“Young birds are vulnerable because they don’t have highly developed flying skills,” Mr. Bonner said. “Hummingbirds are sometimes killed in glass collisions, but they can turn on a dime and get out of the way faster than perhaps a robin or a chickadee or sparrow might.”
High-migrating birds are more likely to hit tall office buildings, but most glass collisions occur at 35 feet and lower, where the birds are feeding and resting.
Research is underway to document places in Pittsburgh where birds are most likely to crash into glass. Since 2014, volunteers patrolling 10 Downtown routes have plotted about 1,200 birdstrike locations as part of a Carnegie Museum of Natural History initiative linked to the American Bird Conservancy.
Luke DeGroote, an avian research coordinator at the Carnegie’s Powdermill Avian Research Center in Westmoreland County, said he’s quietly working with Pittsburgh companies that have bird collision problems to make their spaces more bird friendly.
Powdermill, a 2,200-acre nature preserve near Rector, is home of North America’s longest-running bird banding site. It is also one of the world’s only research and development centers for testing birds’ response to various window treatments and glass mixtures. The other testing facility is in Austria.
Powdermill staff capture birds of all kinds in curtains of mist netting. They measure, weigh and check the birds for parasites and band them for migration studies. The birds are carefully bagged and released into a hole at one end of a 25-foot shed about as wide as a sidewalk. On the other side of the tunnel are two opaque window panels covered in different designs. The birds fly toward the exit, veer toward the window they sense offers the best chance of escape.
Before they crash into the test material they are caught in another net.
Researchers document the species tested and most desirable panel designs supplied by glass manufacturing companies. Each sample is given a score included in the product’s LEED certification, the Leadership in Energy and Environmental Design rating used globally as a measure of environmental suitability.
Some of the products are adhesive overlays with lines or dot patterns. Some involve treatments baked into the glass that create reflectants visible to birds but nearly imperceptible to humans. Mr. DeGroote said that while commercial use of bird-friendly glass can increase the price from 30% to 60%, the market for bird-friendly glass is growing.
“Two reasons: greater awareness of birds hitting windows and collision-monitoring programs like the one we do in Pittsburgh,” he said. “Because of this, more cities or districts are becoming aware of urban bird conservation and creating legislation requiring or suggesting that developers, architects and business build and maintain bird-friendly buildings.”
In December, New York City, located on one of the world’s busiest bird migration routes, narrowly rejected a bird-friendly building glass zoning amendment.
Mr. DeGroote said there are no such ordinances in the Pittsburgh area, but glass-panel overlays have been added to a few structures. In Oakland, the cafe side of the Carnegie Museum of Art is covered with a bird-avoidance adhesive pattern tested and approved at Powdermill. The Frick Environmental Center in Squirrel Hill has LEED-approved windows. Mr. Bonner said Audubon’s Beechwood Farms Nature Reserve in Fox Chapel protects birds from small windows using exterior screens, while two big plate glass windows are covered with bird-deterrent tape and adhesive film.
“One thing you can do at home is leave the screens [in the windows] even in the winter,” he said. “Birdavoidance tape and full-window film are available. I was recently talking with someone from a company that makes bird-friendly window treatments. He said not only does it deter bird death, but people are finding that the films also cut down on cooling bills because it reflects out sunlight.”