Until as recently as the early 1800s, the passenger pigeon was still considered the most numerous bird in all of North America. Individual flocks could contain in excess of a billion individual birds, and would take more than an hour to fly overhead. But as a hugely plentiful source of cheap meat, the birds were hunted in unprecedented numbers: at one nesting site in Michigan in 1878, as many as 50,000 birds were killed every day for nearly five months, and the last surviving flock of 250,000 birds was killed in its entirety by one group of hunters in a single day in 1896. The final individual bird—a female named Martha, who was being held in captivity at the Cincinnati Zoo—died in 1914.