Numbering in the billions, nesting in huge colonies scattered from the Great Plains to the East Coast, and intensely social, the species’ sheer numbers made it seem invulnerable to changes spurred by an industrializing nation.
One 19th-century account estimated more than 2.2 billion birds in a single flock; another calculated 136 million birds in a Wisconsin nesting area. In 1813, John James Audubon reported a migrating flock in Kentucky that passed undiminished for three days overhead: “the light of noon-day was obscured as by an eclipse.”
Yet in the second half of the 19th century, pressed by overhunting and deforestation, Passenger Pigeon populations began to decline. Within a few decades, they became scarce. The species disappeared altogether 100 years ago with the death of Martha, the last known Passenger Pigeon, who died in the Cincinnati Zoo on September 1, 1914.
In hindsight, the path to extinction was not altogether surprising. As vast stretches of hardwood forests were cleared in America’s westward expansion, the birds lost much of their habitat and food supply. The pigeons were hunted indiscriminately for sport and for commerce, killed by the millions and shipped to food markets in the cities. The enormous flocks were easy targets for hunting parties, who could shoot hundreds of birds from the sky in a matter of minutes.
But although many observers noticed the species’ dramatic decline, there was little interest in or understanding of the process of extinction in the 19th century.
Today, with greater recognition of the threats to biodiversity and more sophisticated research tools, scientists can profile species at risk and help shape conservation work. “DNA sequencing and mathematical models can help us determine relatives of species and see how much genetic variability there is in a population or how it differs from another population,” says Associate Curator George Barrowclough, who has studied the endangered Northern Spotted Owl and the California Gnatcatcher. “It shows us how genetically distinct an endangered species is so that we can focus our conservation efforts on saving those that are particularly divergent.”
Might the passenger pigeon ever return? By combining genetic material from extinct species with cells from living species, researchers in the U.S. and abroad are attempting to reverse extinctions. In the case of Passenger Pigeons, this effort involves using closely related Band-tailed Pigeons as surrogates.
In the video below, Curator Ross MacPhee discusses the future of species de-extinction.
A version of this article appears in the Winter 2014 issue of Rotunda, the Member magazine.