Nineteenth-century accounts describe nesting colonies covering many square kilometres and migrating flocks that took hours to pass overhead. Population estimates for the peak are necessarily rough, but the species is generally regarded as having been among the most numerous birds on Earth, with figures on the order of three to five billion often quoted.
Two pressures acted together. Telegraph and rail networks let commercial hunters locate nesting colonies and ship carcasses to distant city markets in bulk, so a colony could be worked out in a single season. At the same time the eastern hardwood forest that supplied the acorns, beechnuts and chestnuts on which the birds depended was being cleared for farmland.
The species also appears to have depended on sheer numbers for breeding success, swamping predators through synchronised mass nesting. Once colonies fell below some threshold, reproduction failed even where birds remained. The last known individual, a captive female named Martha, died at the Cincinnati Zoo on 1 September 1914.