For birds that migrate through the Midwest in the spring and fall, Chicago is an especially deadly city to fly through, with its glass skyscrapers and glittering facades. Ben Goldfarb takes us on a tour of the Windy City’s lethal landscape and introduces us to the conservation volunteers (called monitors) who collect incapacitated and dead birds that have collided with glass, and reports on the measures building owners and architects are taking to make the city safer for our swift winged friends.

Every year, the monitors collect around 7,000 birds, doubtless a tiny fraction of the unknowable number that die every year. Some days the work is constant: One recent October morning, the Monitors scooped up around a thousand birds at McCormick Place, a convention center abutting Lake Michigan whose massive glass façade makes it a particularly egregious hotspot. Prince joked that the volunteers measured their busyness in Valium gulped. “People call and say, hey, is there some kind of disease outbreak going around?” she said wryly. “No, it’s just architectural design.”

In Nuttall’s day, glass was comparatively rare: windows tended to be small and set within brick or granite. Today it’s everywhere—particularly in Chicago, longtime home of the mid-century architect Ludwig Mies van der Rohe, whose preference for vast glass facades still influences the city’s aesthetic. van der Rohe’s purpose, he once said, was to fuse nature, humans, and structures in a “higher unity.” The virtue of glass was that it connected indoor spaces with outdoor ones. The irony is awful: We prize a material that kills birds because it makes us feel closer to nature.

Cheri has been an editor at Longreads since 2014. She's currently based in the San Francisco Bay Area.