Worth almost $1 billion, the new Vikings Stadium may see bloody dots from smashed birds after opening. Environmental group appeals to change type of glass, because birds won’t notice the one used, crashing into it.

When first presented in May 2013, the new Vikings Stadium was advertised with the world’s largest glass roof. The transparent structure was used as a cheaper alternative to retractable cover, but is now under fire from Audubon, a respected environmental NGO.

As Audubon stresses, the design includes highly reflective glass surface of almost 200,000sqf. This kind of glass reflects its surroundings and makes parts of the building invisible for migrating birds. Audubon appealed to the Minnesota Sports Facilities Authority to replace the surface with fritted glass that would make the stadium clear for birds. The alteration would cost as much as $1.1 million.

In a statement to WCCO, MSFA writes: “We were able to adopt operational guidelines used by other downtown office and residential buildings, we were unable to change the design and do not have the budget to include the $1.1 million needed for bird safe glass.”

According to Audubon the insufficient environmental care stands against state guidelines for publicly-funded buildings and the LEED standards. The NGO also claims a change of glass would bring savings in maintenance cost, so the investment wouldn’t be in vain.

MSFA did say yes to some bird protection, agreeing to turn off lights after midnight which attract birds during migration periods. Audubon urges the Authority to do more. Currently almost 30,000 people sent emails with appeals to change the glass.