With homemade signs firmly in hand, a small band of citizen-activists has pushed bird-safe glass at the new Minnesota Vikings stadium from an afterthought to a cause célèbre.

The grass-roots environmentalists and bird aficionados were stirred to action by what they view as an unjustifiable decision to use clear glass on the stadium that won't divert birds from deadly collisions. Since they showed up in force at a Minnesota Sports Facilities Authority (MSFA) meeting last fall, the birders demanded and got attention, but so far no changes.

"There are so many things that can be done — it's just mind-boggling why they have not done any," said Ann Laughlin, a member of the newly created Minnesota Citizens for the Protection of Migratory Birds.

In rejecting their pleas, the Vikings and the MSFA have asserted that it was too late to order new glass, that bird-safe etched glass would hurt the airy aesthetic of the stadium and that it would cost too much.

Michele Kelm-Helgen, chair of the MSFA, said she's working with Maplewood-based 3M and Matthew Anderson, executive director of state chapter of the Audubon Society, toward a solution. 3M is trying to develop a product that would be both transparent and protective of birds.

"We're getting close," she said. "It's been frustrating that we don't have anything to announce yet."

Still, with the glass expected to start going on the $1 billion stadium this month, most activists say they have received a chilly reception from the Vikings, who haven't met with them, and the MSFA. Undeterred, at least a couple of the grass-roots crew members regularly speak during open forums at the MSFA's monthly board meetings. The volunteers promise they're in it for the duration.

"We're tenacious. We're not going to give up," said Wendy Haan, also with the fledgling migratory bird group. "We're going to be picking up those [dead] birds and shaming" stadium officials and the Vikings.

National attention

The homegrown band of activists has helped focus nationwide attention on bird safety. An estimated 400 million to 1 billion birds die annually in building collisions, activists claim.

Elise Morton, a local Audubon chapter member and University of Minnesota postdoctoral student in microbiology says grass-roots activism has its benefits. "It's easier to be passionate and pour yourself into something when it's not your job and there's no bureaucrat," she said.

This fight even has her pondering a career change. "What I struggle with more and more is wanting to do something more applied," she said. "I feel so passionate about this. I wake up thinking about it."

A nature lover who grew accustomed to walks in a park near her home in Bloomington, Ind., Morton went to a Minneapolis Audubon meeting as a means to do some birding and conservation work. On her first day, she heard about the stadium glass.

"It just seemed so wrong and I was so new to everything and fresh, I thought we could make a change," she said. "I never would have imagined this would become half my life."

A Minnesota law took effect in May 2013 that requires newer buildings to make accommodations to protect birds. The Vikings stadium, however, was already deep into the design process at that point and not subject to the law.

Haan worries that the western side of the stadium with its massive pivoting glass doors will be an especially deadly crash site with birds getting confused by nearby trees reflected in the doors. The stadium location is also problematic, they say, because it stands out on the eastern edge of downtown, perilously close to a turn in the migratory Mississippi River passageway.

Saving the vibrant ones

The activist most familiar with how and where birds crash is Audubon Chapter of Minneapolis President Jerry Bahls. During the spring and fall migration seasons, every morning Bahls leads a group of about 20 through downtown Minneapolis collecting dead and injured birds. "You really get a sense for which buildings are good and which are bad," he said.

Bahls, a retired Ph.D. chemist for 3M, developed a fondness for birds while hunting with his dad as a boy. He no longer hunts, but he and his wife are taking a bird-studying trip this month to Cuba, where he hopes to spy a bee hummingbird, one of the world's smallest birds that is found only on that island. He's also been birding in the Arctic, where he saw an albatross with a 7-foot wingspan.

Laughlin, a retired legal writer for Eagan-based Thomson Reuters, volunteers at the Wildlife Rehabilitation Center of Minnesota in Roseville. There she sees birds that have collided with glass and have head or spinal injuries.

"People say, 'I don't see a pile of 100 dead birds a day so there's not a problem,' " Laughlin said, adding that the birds likely have been rescued, picked up by Bahls' group for tracking or "fly away and die or predators get them."

What's particularly poignant for bird lovers is that the birds that collide with buildings are the healthy, young and vibrant ones.

State Audubon director Anderson believes the marketplace will eventually develop a solution because of increased awareness about bird welfare.

"The crazy thing here is we're talking about birds that are 4-6 ounces that travel thousands of miles," Anderson said. Making buildings safer is "in some ways … the least we can do."

Twitter: @rochelleolson