Audubon volunteer and former attorney Jeannine Thiele hikes beneath a skyway in search of dead birds at the Minneapolis College on Tuesday. (Elizabeth Flores/The Minnesota Star Tribune)

As millions of migratory birds travel northward to their ancestral breeding grounds this spring, volunteers with the Audubon Chapter of Minneapolis are hitting the streets of downtown Minneapolis, looking for victims of window strikes.

Their objective: to determine whether a 2016 city ordinance requiring new skyways to have bird-safe glass is working as intended.

Jeannine Thiele, vice president and chair of Audubon’s conservation committee, has started each morning of May searching for dead and injured birds. She checks around the two skyways at Minneapolis College on the edge of the Loring Park neighborhood — one of them old, one new.

So far this spring, Audubon volunteers have found more dead birds at the school than around any other location — all around the older skyway, which was built before the bird-safe-glass rules took effect.

Thiele said she suspects the reason for the many deaths is the highly reflective windows, coupled with a decorative glass panel that juts out over the leafy Loring Greenway, confuse birds into thinking they’re aiming for the bushy vegetation nearby instead of an unrelenting barrier.

“That part that hangs off like that, if you were trying to design something to kill birds, that’s what you would do, just suspend that piece of glass out in midair,” Thiele said. “Not only do they not see the reflection, but they just see through the glass. We can see the frame and the smudge marks, but a bird isn’t able to analyze those cues.”

Thiele keeps a stack of Chinese food takeout boxes in her tote bag to collect dead birds. On Tuesday morning, she scooped up two white-throated sparrows and two Tennessee warblers near the college’s older skyway.

Jeannine Thiele of the Audubon Chapter of Minneapolis collects dead birds she found beneath a skyway at Minneapolis College on Tuesday. Thiele spent part of her childhood in the country, where she learned to appreciate birds. She said when she was anxious or stressed, she would “go sit out on this tree snag in the marsh and just listen to all the song.” (Elizabeth Flores/The Minnesota Star Tribune)

During peak migration traffic last week, nearly 40 million birds were in flight across Minnesota, according to the BirdCast migration tracker. A new study in the Wilson Journal of Ornithology suggests that annual bird deaths from window strikes could be at minimum 1.3 billion in the United States.

The dead birds that Aubudon volunteers salvage are taken to the Bell Museum in St. Paul, where they can be used for educational and research purposes. They can be archived as skeletons or stuffed skins, with their tissues screened for contaminants so scientists can predict new animal diseases as well as the next pandemic in humans, said Sushma Reddy, the Bell’s Breckenridge Chair of Ornithology.

The few injured birds head to the Wildlife Rehabilitation Center of Minnesota in Roseville.

Tami Vogel, the center’s executive director, said 72% of birds that appear to survive the initial collision eventually die because of severe fractures — especially involving joints, which can’t be repaired — and brain damage that destroys a bird’s sense of balance.

The Wildlife Rehabilitation Center documents every bird-glass collision victim that passes through its doors. Records show a concussed-looking yellow warbler treated there flew more than 2,800 miles before hitting a window. A crippled Swainson’s thrush made it nearly 5,000 miles.

“They’ve flown through all sorts of natural and manmade obstacles and other cities to get this far in their migration only to hit a window,” Vogel said. “And it can be so easily avoided. I think that’s the frustrating thing.”

The center recommends a range of products that homes and businesses can use to bird-proof windows. But the simplest, most inexpensive solution is to use decals that reflect UV light, which is invisible to the human eye but can be seen by birds.

Jeannine Thiele of the Audubon Chapter of Minneapolis says the bird population is in serious decline. Here she searches for dead birds beneath a skyway at Minneapolis College on Tuesday. “Since 1970, we’ve lost 30% of the net population of birds,” Thiele said. (Elizabeth Flores/The Minnesota Star Tribune)

Promising findings

Audubon’s initial data suggests that the 2016 Minneapolis ordinance is working. Volunteers haven’t yet found any dead birds beneath the skyways built since then. But they’ll keep looking through the spring migration and resume monitoring the fall migration, when birds will move southward with the chicks they raise this year.

Volunteer monitor Roseanne Meier said that as sad as it has been to collect bird strike data as a bird lover, the project has been an opportunity for her to contribute to science by observing birds closer than she could ever get to a live animal.

“We know that there are places where they are hitting consistently,” Meier said. “Skyways just seem to be like a very specific place where we could make such a big difference. We can do something to that skyway that’s proven to be effective, and we can save all those birds’ lives just in that one place.

“And that’s what I hope for us in the future, that when we have identified a problem, we do something about it.”

Minneapolis College spokeswoman Kathy Rumpza said the school has been talking with community members about bird safety measures on campus. Now under construction, its newest skyway will incorporate a bird-safe glass made by Viracon.

“We are considering options related to other glass facades, including adding branding or other elements that could improve bird safety,” Rumpza said.

Readers interested in volunteering as citizen scientists for this and future monitoring projects can contact admin@audubonminneapolis.org.

Audubon volunteer Jeannine Thiele collects a dead bird she found beneath a skyway at Minneapolis College on Tuesday. (Elizabeth Flores/The Minnesota Star Tribune)