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Study Tallies Bird Deaths at Glass Stadium

Friday, March 3, 2017

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A new informal study conducted by three conservation groups has found that the U.S. Bank Stadium in Minneapolis is as deadly to birds as people feared.

"We knew that the glass would be highly confusing to the birds," volunteer Jim Sharpsteen told City Pages. "They see a reflection of a blue sky in the glass, they think it's a blue sky. They see reflections of trees, they think they can land in those reflections of trees.

"This confirmed what we already believed would be bad."

Darb02, CC-BY-SA 4.0, via Wikimedia Commons

From August 2016 (when the stadium opened) to November, volunteers from the Audubon Chapter of Minneapolis and other groups walked around the U.S. Bank Stadium looking for carcasses of birds that had flown into the 200,000 square feet of reflective glass.

The stadium had been a concern, not just because of its glass facade, but also because it’s located in the Mississippi Flyway, a bird migration route that stretches from Canada all the way down to South America.

The Minnesota Department of Natural Resources had urged the Minnesota Sports Facilities Authority to consider bird-friendly designs from the building’s inception, but the $1.1 billion facility was made with highly reflective glass instead.

The Survey

In an 11-week span, from August 2016 (when the stadium opened) to November, volunteers from the Audubon Chapter of Minneapolis, the Minnesota Citizens for the Protection of Migratory Birds and the Friends of Roberts Bird Sanctuary walked around the 1.75 million square feet of stadium looking for carcasses of birds that had flown into the 200,000 square feet of reflective glass.

White-throated Sparrow
© iStock.com / BrianEKushner

Conservation groups found White-throated Sparrows and other species dead and stunned around the stadium, the study said.

The study took place (almost) every day between 6 a.m. and 8 a.m. around the perimeter of the building. During the observation period, with those restrictions, volunteers found 74 birds of 21 species. Of those birds, 60 were dead and 14 were observed stunned on the ground or in the air after colliding with the glass.

White-throated Sparrows were found most often (33 percent), followed by Ruby-throated Hummingbirds (12 percent), according to the study data.

Five of the species killed or injured are included in Audubon Minnesota’s Blueprint for Minnesota Bird Conservation 2014 list of priority breeding species (birds identified as declining in Minnesota, dependent on vulnerable habitat, or both). These species include the Common Yellowthroat, Least Flycatcher, Marsh Wren, Ovenbird and Vesper Sparrow. Another species, the Snow Bunting, had never previously been found as a casualty from collisions with other Minneapolis buildings.

What Does This Mean?

To put the 60 avian deaths in comparison, the previous highest mortality recorded for a single building in Minneapolis averaged 42 birds per migration period.

If those 60 documented deaths remained consistent in future spring and fall migrations, the U.S. Bank Stadium would cause approximately 360 bird deaths over the span of three years, the conservation groups say.

Tony Webster, CC-BY-SA 2.0, via Wikimedia Commons

The report concludes with suggestions to reduce the number of bird collisions, which includes etching patents on the glass, a solution similar to what the Jacob Javits Center in Manhattan did. In that instance, collisions were reduced by 90 percent.

However, these estimates don’t consider the fact that the study’s recorded numbers are likely underreported.

The volunteers’ limited access to places like upper ledges, patios and rock beds; combined with security, maintenance staff and the general population removing birds; and the likelihood that some carcasses were picked up by scavenger animals before they could be reported, all contribute to an unknown additional number of deaths.

What Next?

The report concludes with suggestions to reduce the number of bird collisions, which includes etching patents on the glass, a solution similar to that employed at the Jacob Javits Center in Manhattan. In that instance, collisions were reduced by 90 percent.

The findings were meant to serve as a guideline for an official, $300,000 survey scheduled to take place between this spring and 2019.

They were also a vehicle for one last plea to the MSFA board to take action on a bird-safe solution before the official survey is done, a push they made when they presented to the board on Feb. 27.

Despite having a new chairwoman (the previous regime of Michele Kelm-Helgen fought against re-doing the glass before a study was done), Kathleen Blatz, the board took no action after listening to the study findings.


Tagged categories: Building design; Building envelope; Design; Design build; Environmental Protection; Glass; Infrastructure; Stadiums/Sports Facilities

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