Pigeons and Doves

One of the most famous examples of an extinction caused by humans involves the passenger pigeon. This species became extinct in the early twentieth century through gross overhunting coupled with the loss of most of its natural habitat of mature angiosperm forests, which was widely converted to agriculture.

The natural range of the passenger pigeon was southeastern North America. Prior to its overhunting, about 300 years ago, the passenger pigeon may have been the world's most abundant landbird. Its pre-impact population has been estimated at three to five billion individuals, which may have accounted for one quarter of the population of all birds in North America.

During its migrations, the passenger pigeon occurred in tremendous flocks that were described as obscuring the sun on an otherwise clear day, and could take hours to pass. In 1810, Alexander Wilson, an American naturalist, guessed that a single migratory flock, perhaps 0.3 mi (0.6 km) wide and 89 mi (144 km) long, contained two billion birds. Many other impressions written by naturalists of those times also suggest that the passenger pigeon was an extraordinarily abundant bird.

Because passenger pigeons tended to migrate and breed in large, dense groups, it was easy for commercial hunters to kill them in large numbers and then sell the carcasses in urban markets. The passenger pigeon was slaughtered in enormous numbers using guns, clubs, nets, and smoke. The size of some of the hunts is astonishing, for example, in 1869 an estimated one billion birds inhabited Michigan alone. This intensity of exploitation, occurring at the same time as the destruction of much of its breeding habitat, proved to be unsustainable, and the passenger pigeon quickly declined in abundance. The last known nesting attempt in the wild occurred in 1894, and the last passenger pigeon died in a zoo in 1914.

The extinction of the passenger pigeon has become a metaphor for the sorts of damages that uncontrolled exploitation by humans can cause to even enormously abundant ecological resources.