The Passenger Pigeon or Wild Pigeon (Ectopistes migratorius) is an extinct North America bird. The species lived in enormous migratory flocks until the early 20th century, when hunting and habitat destruction led to its demise. One flock in 1866 in southern Ontario was described as being 1 mile wide and 300 miles long, took 14 hours to pass, and held in excess of 3.5 billion birds. That number, if accurate, would likely represent a large fraction of the entire population at the time.
Some estimate 3 to 5 billion Passenger Pigeons were in the United States when Europeans arrived in North America. Others argue the species had not been common in the pre-Columbian period, but their numbers grew when devastation of the American Indian population by European diseases led to reduced competition for food