RECTOR, Pa. (AP) - A cluster of little cotton bags, cinched at the top, hangs from a carabiner along a narrow, 25-foot-long shed. Every few seconds, a bag bounces.
Mallory Sarver unhooks one, loosens the drawstring, reaches in and pulls out a tiny bird with a gray head, a brilliant yellow belly with black streaks and white stripes on its black wings.
“Magnolia warbler,” she tells a video camera set against a hole at the shed’s entrance. She reports the bird’s banding number, too, then releases the bird into the shed through a sleeve.
The interior is a tunnel. Researchers at the Powdermill Avian Research station use it to test how birds respond to various window treatments. At the end of the tunnel - behind a safety net - two panels sit side by side, one etched with opaque designs such as wavy lines or polka dots, the other a clear pane.
Ideally, the test panels that the birds avoid flying toward most often become commercial windows favored by builders, architects and homeowners. Hundreds of millions of birds are injured or killed in this country each year in collisions with clear windows that look, to them, like the trees and sky they reflect.
Powdermill, a program of the Carnegie Museum of Natural History, has been testing manufacturers’ products since 2009.
The research extends to Downtown Pittsburgh, where staff and volunteers patrol 10 routes looking for dead birds. They add their findings to the database.
The focus is on birds migrating in spring and fall, stopping here between north and south destinations. Think of them as unknowing out-of-towners compared to our street-smart local sparrows, pigeons and doves that rarely crash.
Powdermill is 2,200 acres of woodlands and wetlands. Throughout, 65 curtains of mist nets are rigged to catch birds. They hit the net and plop into its pouches.
Every hour or so, a crew traipses the paths to collect them. Those that haven’t been banded are bagged and carried to the banding station. There, they are banded, measured, weighed and checked for parasites. An intern enters the information into a database for Powdermill and its worldwide research network.
It is a bonus day for magnolia warblers, as Sarver pulls one after another from a bag. It’s a hard heart that inures to seeing a magnolia warbler, but a gray catbird changes the dynamic, cranking out its full rebuke before Sarver can even get it out of the bag.
Not every bird is run through the tunnel. Luke DeGroote, avian research coordinator, says birds with unusual flight traits, such as flycatchers, would risk injury.
On one net check, he greets Eugene Hood, who is carrying cotton sacks back to the banding station. He opens one and shows DeGroote a prairie warbler, an almost fully brilliant yellow bird flecked in black.
“Wow,” DeGroote says. “We don’t get many of these.”
The prairie warbler prefers grasslands and shrubs, and in migration, “they like scrubby habitat,” he says.
Anomalies aside, America’s changing landscapes have changed migration patterns. The clearing of forests as humans migrated west in the 18th century led to an agrarian society of the 19th century that favored birds like the northern bobwhite, while the golden-winged warbler declined with deforestation.
“We have learned the importance of habitats that are as diverse as possible,” says DeGroote.
At the same time, bird advocates encourage cities to establish lights-out policies at night, when birds travel, using the moon and stars to navigate. City lights obfuscate these natural guides, drawing birds into canyons surrounded by glass.
“Lights and window glass are overlapping concerns,” DeGroote said.
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The test tunnel is equipped with monitors that record each flight and light conditions.
“We want to see if what happens on a sunny day also happens on a cloudy day, and what works for any bird,” Sarver said.
Before Powdermill tests a window product, it puts enough birds through the tunnel toward a neutral background - one of them imitates a cloudy sky - until the same number of birds has chosen each side. Then a test pane is inserted beside a clear pane. Most window designs are unobtrusive to humans.
Roughly 20 percent of the test flights are not usable because the bird doesn’t always choose a side. Some hop to the floor, some go to the ceiling.
The tunnel swivels to stay in line with the sun and has an array of mirrors on one end.
“The mirrors reflect sunlight onto the window so that it gets the same illumination you would get from an actual window in place,” John Wenzel, director of the Powdermill Nature Reserve, said. “If we didn’t have mirrors, the bird would be coming from one side and the light would be coming from the other, which is not a valid test.”
The American Bird Conservancy rates products based on the tunnel tests, with the caveat that no product eliminates the risk. It also suggests materials people can apply to their windows, such as decals, blinds and exterior screens. For more information on those solutions, visit the American Bird Conservancy.
One product rated on the site is Walker Glass’ Aviprotek, with which the National Aviary is replacing the windows in its Tropical Rainforest.
Chris Sheppard, director of glass collisions programs for the American Bird Conservancy, was curator of birds at the Bronx Zoo when she got a grant to do tunnel testing with Powdermill in 2009.
“We needed to do this work with a lot of birds,” she says. “The tunnel scores are an index, a way to compare one glass to another.”
Daniel Klem, a professor of ornithology and conservation biology at Muhlenberg College, is the first scientist known to have devoted his work to preventing bird collisions with glass, in the 1970s. He has some issue with Powdermill’s methods.
“I am a supporter of what they are doing,” he says, “Like all things, it is a work in progress. But my concern is that people will embrace this kind of testing as the industry standard. Tunnel tests can tell you a lot of things. They have a utility. But these windows aren’t in real buildings.
“And how can you be sure the bird was not influenced by the netting?”
Wenzel acknowledges the tunnel test has limitations but, if anything, Powdermill errs on the conservative side.
“The bias you introduce is that the bird in its urgency to get out of the tunnel would fly to the gap that it wouldn’t go to if it wasn’t in a tunnel,” he says, using the example of bars on the window of a jail cell. A bird outside would see the vertical stripe design and avoid it, but a bird trapped inside would seek escape through the bars. “Anything that performs well in a tunnel would perform even better in nature when it isn’t looking to escape.
“We have plenty of people looking over our shoulder at this instrument, and it’s still the best thing we’ve got.”
“We can’t replicate nature,” says Sheppard, “but we are trying to come up with some kind of standard to give the birds a choice.”
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Information from: Pittsburgh Post-Gazette, http://www.post-gazette.com
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