Testing of a bird repellent that smells like grape Kool-Aid at U.S. Bank Stadium was canceled Thursday because of objections from conservation group Audubon Minnesota.

Minnesota Sports Facilities Authority (MSFA) officials installed three BirdBuffer boxes earlier this month atop 425 Park Av., a concessions building across the street from the stadium's signature western facade. The aim was to discourage migratory birds from gathering in the area and colliding with the stadium glass.

Stadium officials had planned to discuss the boxes Thursday at the MSFA's monthly meeting. Instead, Chairman Michael Vekich announced they were canceling the testing for now because of concerns raised by Audubon Minnesota executive director Rob Schultz.

Schultz, who didn't attend the meeting, sent a strongly worded letter Wednesday stating that the science and effectiveness behind BirdBuffer is unproven and potentially dangerous to humans and animals.

"As such, we feel it is difficult to justify the use of public funding being used for this purpose," he wrote.

Environmentalists have persistently sounded the alarm about the hazards of the glass on U.S. Bank Stadium since before construction began on the 5-year-old, $1.1 billion building. They initially urged that the building's glass be etched as a means to keep birds from deadly or harmful collisions. At the time, the proposal was dismissed as deleterious to the building's airy aesthetic.

In November 2019, the MSFA received the results of an Oklahoma State University-led study about bird collisions in downtown Minneapolis. The $300,000 peer-reviewed study, paid for by the MSFA and the main stadium tenants, the Minnesota Vikings, found that four downtown buildings — including U.S. Bank Stadium — accounted for 74% of bird collisions and 68% of bird fatalities among 21 buildings surveyed.

The study found three main problems causing bird injuries and death: lighting in and around buildings at night, expanses of reflective glass, and vegetation near glass that causes birds to see trees reflected in it and believe they're flying into habitat.

Options listed in the study included three products applied to the glass exterior that ranged in price, depending on the amount of coverage, from $40,000 to $570,000. Those prices didn't include labor and installation, which are expected to at least double the cost.

Two years ago, when Schultz presented to the MSFA the final report from Oklahoma State, he urged that film be placed on the glass to make it visible to birds. Now Schultz wants the MSFA to revisit the study's recommendations, including treating the glass, along with ditching BirdBuffer.

Vekich said that testing BirdBuffer made sense, based on information from the company. But in his letter to the MSFA, Schultz wrote that he was skeptical of BirdBuffer's claims that the ingredients in the grape-scented "avian control" compound were safe. He noted the company identifies 20% of the chemical weight as methyl anthranilate while 80% remains a trade secret.

"We question the judgment of spraying undeclared chemical substances into the air; the moral implications of birds, wildlife and people being unknowingly exposed to it; and the legal risks if the chemical is later deemed to have previously unknown side-effects or dangers," Schultz wrote.

According to the website for Mukilteo, Wash.-based BirdBuffer, the liquid bird repellent is made from concentrated grape skin extract that is safe for humans and animals. When in use the scent is said to be discernible from the sidewalk, though not strong or unpleasant. A company official didn't immediately respond to a request for comment.

The MSFA, which oversees the stadium on behalf of the public, spent just under $5,000 on the three trial boxes outside the stadium. It planned to test the product and then install more boxes in time for the spring migratory season in March.

But that plan is off for now, with no other plan in place to mitigate bird deaths and injuries.

Keith Olstad, who chairs Audubon Minneapolis, said at Thursday's meeting that the MSFA should consider retrofitting the glass to make it visible to birds.

"Let's refocus our efforts on the most effective and affordable options," he said.

Constance Pepin, another Minneapolis environmentalist, also advocated retrofitting the glass to help birds avoid collisions, saying it would enhance the building's design as etchings and art have done for several glass skyways throughout downtown.

In her testimony, advocate Ann Laughlin pushed for similar mitigation and referred to a dead yellow-throated warbler she had placed on the table when she last spoke before the board — a bird she said she had found on the ground that morning outside U.S. Bank Stadium.

Laughlin said Thursday that she wasn't trying to shock the MSFA members. "I just wanted to show you, to drive home what happened outside the stadium," she said of the dead bird.

Vekich spoke with the three environmentalists after the meeting and said he takes their input seriously. "I think good discussion has come out of this," he said.

Vikings vice president Lester Bagley attended the meeting but left before the public testimony was finished.