The nighttime glow of downtown Minneapolis may make for a picturesque skyline. But it is also a distinct threat to the 250-plus bird species that migrate through the state along the heavily trafficked Mississippi River Flyway.
That’s according to new research from Cornell Lab of Ornithology, which recently ranked the city among the 10 most dangerous metropolitan areas for migrating birds, based on light pollution levels combined with bird migration density. Minneapolis was labeled the sixth-most dangerous city for spring migration, and seventh for fall migration. Chicago, Houston and Dallas were 1-2-3 in both seasons.
“[The research] really is pointing out how important that Mississippi Flyway is, and how cities that are placed in sensitive positions on there really are important to birds,” said John Rowden, director of community conservation for the National Audubon Society.
Many birds migrate at night, Audubon Minnesota explains, and the artificial light from cities can short-circuit their navigational system. Birds can be drawn to the brightness and end up smashing into the side of a building, or become confused and fly in circles until they’re exhausted and fall to the ground. Lit windows can also cause collisions, as birds see it as a passageway. One 2014 report estimates between 365 and 988 million birds are killed annually in the U.S. as a result of window collisions.
Audubon Minnesota Communications Manager Ashley Peters said while she isn’t aware of any Twin Cities-based studies measuring the impact of Lights Out, there is evidence it has a positive effect. One notable study comes from Chicago, where researchers found an 80 percent decrease in bird collisions when one complex of buildings, McCormick Place, turned off its lights overnight. “We know enough to say that this does work, it does have an impact,” Peters said.
Bird-friendly architecture is also getting more consideration, said Doug Bergert, senior project designer at Perkins+Will, which designed the Bell Museum’s new building.
A key goal for that project was to minimize its potential impact on birds, said George Weiblen, Ph.D., the museum’s science director. “As a natural history museum, it’s our mission to communicate that we are a part of nature,” he said. “Our challenge is, how can we support ourselves and maintain the healthy environments we depend on?”
To address artificial light concerns, Perkins+Will chose light fixtures that don’t “attract birds or distract them,” Bergert explained. Exterior lighting around the museum points toward the ground rather than into the air. Inside, motion sensors ensure rooms go dark when not in use.
In addition, the building’s glass has low reflectivity, and includes frit patterns that aren’t obtrusive to humans, but can be seen by birds. ”It’s not a problem that is gonna go way,” Bergert said of bird collision. “More and more people are aware of this issue and they don’t want to ignore it.”
For those people, Perkins+Will and Audubon Minnesota created a bird-safe building guide. But Peters argued addressing the issue in piecemeal fashion is challenging. “What we really need is widespread standards or Lights Out policies that will be much more likely to have an effect than building-by-building, voluntary guidelines,” she said.
Some of that is already happening. Buildings owned or leased by the state are required to turn off lights overnight during migratory periods. And all building projects that receive general obligation bond funding from the state must follow sustainable building guidelines known as B3, which include a number of bird-friendly rules such as Lights Out participation.
But both projects also reflect the current situation in the Twin Cities: that it’s generally up to individual property owners to decide how much of a priority deterring bird collisions is. “Being aware whenever we’re building something that, ‘Hey, we’re situated right in the middle of North America’s largest migratory flyway,’” said Weiblen, “that’s a critical consideration.”