The new Minnesota Viking's football stadium, with its large glass windows, could be a "death trap" for birds that fly through the area during their annual migration, the Audobon Society warned.

The group says that birds from more than 125 migratory species have suffered fatal collisions with buildings in the Twin Cities area since 2007. According to scientists from the US Fish and Wildlife Service and the Smithsonian Institution, up to 988 million birds are killed by such collisions each year in the United States.

And with 200,000 square feet of glass featured in the stadium, it's no wonder Audobon officials are concerned for the birds' safety.

"We're talking about a billion dollar stadium here, and the cost to save perhaps thousands of migratory birds," Audubon Minnesota Executive Director Matthew Anderson said in a statement.

"The Vikings recently approved spending millions and millions of additional dollars to make sure the stadium is 'iconic' - surely they also want to make sure it's not a death trap," he added.

Audubon first met with the Minnesota Sports Facilities Authority (MFSA) and representatives of the Vikings back in May 2013, after the design of the billion-dollar stadium was unveiled. They suggested special glazing techniques and lighting be incorporated into the design to make the stadium safe for birds - advice backed by Minneapolis City Council.

The Audubon groups says it has worked with building owners for years to protect birds, and while some lighting improvements in the stadium design will be helpful, they can't get changes made for the stadium glass.

"We are grateful that the MSFA will be incorporating some of our recommendations regarding lighting design and operations, but lighting is just one part of the problem" said Joanna Eckles, bird-friendly communities' manager for Audubon Minnesota. "The huge expanses of glass, especially facing a new park, are a real cause for concern. Our request was that they meet either the state requirement or the nationally recognized LEED standard for bird safety. In the end, they did neither."