Why the passenger pigeon went extinct and whether it can and should be brought back.

Men still live who, in their youth, remember pigeons; trees still live who, in their youth, were shaken by a living wind. But a few decades hence only the oldest oaks will remember, and at long last only the hills will know.”

—Aldo Leopold, “On a Monument to the Pigeon,” 1947

In May 1850, a 20-year-old Potawatomi tribal leader named Simon Pokagon was camping at the headwaters of Michigan’s Manistee River during trapping season when a far-off gurgling sound startled him. It seemed as if “an army of horses laden with sleigh bells was advancing through the deep forests towards me,” he later wrote. “As I listened more intently, I concluded that instead of the tramping of horses it was distant thunder; and yet the morning was clear, calm, and beautiful.” The mysterious sound came “nearer and nearer,” until Pokagon deduced its source: “While I gazed in wonder and astonishment, I beheld moving toward me in an unbroken front millions of pigeons, the first I had seen that season.”

These were passenger pigeons, Ectopistes migratorius, at the time the most abundant bird in North America and possibly the world. Throughout the 19th century, witnesses had described similar sightings of pigeon migrations: how they took hours to pass over a single spot, darkening the firmament and rendering normal conversation inaudible. Pokagon remembered how sometimes a traveling flock, arriving at a deep valley, would “pour its living mass” hundreds of feet into a downward plunge. “I have stood by the grandest waterfall of America,” he wrote, “yet never have my astonishment, wonder, and admiration been so stirred as when I have witnessed these birds drop from their course like meteors from heaven.”

Pokagon recorded these memories in 1895, more than four decades after his Manistee River observation. By then he was in the final years of his life. Passenger pigeons, too, were in their final years. In 1871 their great communal nesting sites had covered 850 square miles of Wisconsin’s sandy oak barrens—136 million breeding adults, naturalist A.W. Schorger later estimated. After that the population plummeted until, by the mid-1890s, wild flock sizes numbered in the dozens rather than the hundreds of millions (or even billions). Then they disappeared altogether, except for three captive breeding flocks spread across the Midwest. About September 1, 1914, the last known passenger pigeon, a female named Martha, died at the Cincinnati Zoo. She was roughly 29 years old, with a palsy that made her tremble. Not once in her life had she laid a fertile egg.

This year marks the 100th anniversary of the passenger pigeon’s extinction. In the intervening years, researchers have agreed that the bird was hunted out of existence, victimized by the fallacy that no amount of exploitation could endanger a creature so abundant. Between now and the end of the year, bird groups and museums will commemorate the centenary in a series of conferences, lectures, and exhibits. Most prominent among them is Project Passenger Pigeon, a wide-ranging effort by a group of scientists, artists, museum curators, and other bird lovers. While their focus is on public education, an unrelated organization called Revive & Restore is attempting something far more ambitious and controversial: using genetics to bring the bird back.

 Huge flocks of passenger pigeons once roamed North America. Larger than the mourning dove-which it resembled, the passenger pigeon derived its name from an Indian word meaning “wanderer” or one who moves from place to place. Flying at a normal speed of sixty miles per hour, the pigeon moved hundreds of miles in migration and 50-100 miles a day during the nesting season, searching for food.
The largest nesting on record anywhere occurred in this area in 1871. The nesting ground covered 850 square miles with an estimated 136,000,000 pigeons. John Muir described the passenger pigeons in flight, “I have seen flocks streaming south in the fall so large that they were flowing from horizon to horizon in an almost continuous stream all day long.”
Many reasons have been given for the extinction of the passenger pigeon. Ea