An estimated 2 billion birds darkened the sky above John James Audubon's head in the autumn of 1813, a flock of passenger pigeons more than 50 miles long that would take three full days to pass out of view. "The birds poured in in countless multitudes," Audubon wrote. "The air was literally filled with pigeons; the light of noonday was obscured as by an eclipse; the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose."
When Dr. Andrew Stern visits schools to teach children about the now-extinct passenger pigeon, he slowly dims the lights, turning up a radio until the sound of white noise shakes the building.
"It's a little scary," Stern said. "That’s what it was supposed to be like. More [birds] than is imaginable. The fact that they were gone in a little over 50 years is astounding."