It didn't happen with the Vikings stadium, but the installation of bird-safe glass will now be considered for Minneapolis' skyway system.

City council members Cam Gordon (ward 2) and Linea Palmisano (ward 13) want to change city rules so that new or renovated skyways are equipped with bird-friendly glass in the future, according to a council agenda.

"Skyways pose a large threat than people would imagine," Gordon said, according to the Star Tribune, with Palmisano saying that the skyway system's 50-foot height puts it at the same level as bird migratory patterns, yet appear safe for them to fly through.

But the newspaper notes that changing city ordinances for such a reason could increases costs for downtown developers, and "change the aesthetic," airy feel of the city's 8-mile skyway system.

Gordon and Palmisano intend to raise the issue at the next city council meeting.

It follows a lengthy and controversial battle over the glass used on the $1 billion Vikings Stadium in downtown Minneapolis, which conservation groups wanted to be built using bird-safe material.

This was opposed by the Minnesota Sports Facilities Authority and ultimately rejected as it argued it would drive up the cost of the project by $60 million, although bird advocates argued the cost would be as little as $1 million.

Minnesota's Audubon Society says that birds are vulnerable from glass buildings during the day as they do not always appear as obstacles on flightpaths, while lit-up glass buildings attract those flying at night.

Over the past eight years, the society has been monitoring a handful of glass buildings in Minnesota, during which time it has found more than a 100 species of bird dead near them.

A study by the University of Minnesota's Bell Museum of Natural History found that 44 percent of all bird deaths in St. Paul were caused by just two buildings along the migratory path it was monitoring, while in Minneapolis two buildings accounted for 67 percent of deaths.