The Passenger Pigeon ()became extinct in 1914, after the last individual, Martha, died in captivity in the Cincinnati Zoo. It is impossible to imagine that the passenger pigeon, which was one of the most abundant bird species on Earth to become extinct, and there is none left for us to see and observe today. A single flock of passenger pigeons could have 2 billion birds or more, and there were mutiple flocks in the United States, before its decimation. Their nesting colonies in northeastern deciduous forests could be 20 miles across, with so many birds per tree that the branches broke from their weight. It is hard to imagine, however it is true.

The passenger pigeon was driven to extinction by uncontrolled commercial hunting for their meat, which was desired by Euroamerican settlers. The pigeons' migration and nesting behavior made them easy to hunt in large numbers. They were netted, shot and smoked out of trees with sulfur torches. Special firearms, including a forerunner of the machine gun, were used to harvest these birds in quantity. The growth of commercial enterprises was facilitated by the railroads, which made it possible (and profitable) to transport the meat quickly to urban centers. By 1850, several thousand people were employed in the passenger pigeon industry. In New York, one operation processed 18,000 pigeons each day in 1855. In one year in Michigan alone, a billion birds were harvested.

The population collapsed. After 1880, it was no longer profitable to hunt them since they were widely dispersed across the continent. This scattered distribution, however, may also have contributed to the passenger pigeon's ultimate demise by interfering with breeding abilities. The scattered distribution of remaining individuals by mad it more difficult to find suitable mates although some species have been able to recover from a low number of individuals.

Also, without their swarming flocks, the pigeons also may have had trouble competing with other birds for nest sites, and nest sites may have been fewer as the deciduous forests were cut down. The passenger pigeon continued to decline and was extinct in the wild by 1900. Captive breeding efforts were not successful and the last individual died in 1914.

The reasons that the passenger pigeon was unable to recover from the period of overexploitation are not fully known. Although commercial hunting did not directly kill the last passenger pigeon, it sent the species into an extinction vortex from which it could not recover.