In a volume of his American Ornithology, pioneering naturalist Alexander Wilson described a flock of Passenger Pigeons that he had witnessed in the early 1800s as the birds flew between Kentucky and Indiana. The flock, Wilson estimated, numbered 2,230,272,000 birds. “An almost inconceivable multitude,” he wrote, “and yet probably far below the actual amount.” The multitude spanned a mile wide and extended for some 240 miles, consisting of no fewer than three pigeons per cubic yard of sky… if Wilson’s flock had flown beak to tail in a single file the birds would have stretched around the earth’s equatorial circumference 22.6 times… With their powerful chests and long, quick-snapping wings, the pigeons flew an average of 60 miles per hour for hours at a time. Sometimes the swift and seemingly endless flocks stretched across the entire dome of sky, so that wherever one looked, horizon or zenith or somewhere between, there flew the pigeons. They closed over the sky like an eyelid.
