This male passenger pigeon may be the only one you will ever see. Up until the 19th century, it was the most abundant bird in North America, with a population estimated at 3-5 billion. They migrated in enormous flocks, flying as fast as 62 miles per hour. Their numbers declined a bit from 1800—1870 due to deforestation, but the main culprits behind their extinction were humans. They were hunted relentlessly from 1870—1890 and pigeon meat was sold commercially as cheap food. The last confirmed wild bird was shot in 1900 and the last captured bird died in 1914 at the Cincinnati Zoo.