Image: John James Audubon's passenger pigeon portrait/Toronto Public Library.
Passenger pigeons were once the most abundant birds on the planet. The sheer number of them astonished onlookers, and their migrations were recorded with awe and reverence by many early naturalists.
“The air was literally filled with pigeons,” John James Audubon recalled in his 1813 essay, “The Passenger Pigeon.” “The light of noon-day was obscured as by an eclipse; the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose.”
When Audubon wrote that passage, billions of pigeons dominated the North American skies. Flocks were as large as 300 miles across, and could blot out the sun for hours. They were as awesome a natural force as the geysers of Yellowstone or the mesas of the Southwest. It would have been completely inconceivable to Audubon that in 100 years time, only one individual pigeon, raised in captivity, would still be living.
Named Martha after the first First Lady, the last passenger pigeon was a featured attraction at the Cincinnati Zoo. When her only known compatriot died in 1910, Martha became a zoological celebrity for her endling status. The zoo catered to her every need, and Martha lived to the ripe old age of 29 before dying of natural causes on September 1, 1914.
Martha on display in 1967. Image: Smithsonian Institute.
Now, the Smithsonian Institute is bringing her back. To commemorate the centennial of her species' swift extinction, Martha's preserved body will be on display at the Smithsonian starting this Tuesday, June 24.
There has never been a better time to remind everyone that humans have the power to edge out a ubiquitous species over the course of a few decades. Indeed, environmental scientist Will Steffen has argued that the “Anthropocene,” the age of a human-shaped planet, should be considered a distinct ecological era.
According to him, species are being snuffed from existence at a rate of 100 to even 1,000 times the expected percentage, and it may well be accelerating. “When humans look back, the Anthropocene will probably represent one of the six biggest extinctions in our planet's history,” Steffen said to the BBC.
But while there's no question that manmade interference, like over-hunting and habitat encroachment, were the main drivers behind the passenger pigeon's extinction, a recent study revealed that the population had always been unsteady.
In anticipation of the centennial, a team of researchers based out of the National Taiwan Normal University investigated the natural forces that shaped the pigeon population spanning 21,000 years. The results were recently published in the Proceedings of the National Academy of Sciences, and demonstrate that the population yo-yoed wildly year to year.
“Specification on mast crops gives the passenger pigeon a chance to grow up to a number of billions,” lead author Chih-Ming Hung told me. “But it also makes it likely to experience population fluctuations following the cycle of mast crops.
“A high reproduction rate combined with large flock sizes can make a really large population size," he said. "By contrast, such behaviors also make them subject to diseases and negative-feedback ecological effects; they can make serious physical damage to the forest owing to large flock sizes.”
Avian biologist Robert Zink co-authored the study, and also emphasized the species reliance on the whims of bumper crops. “The bottom line is food,” he told me. “The main food, acorns and chestnuts, were likely highly cyclic and unpredictable from area to area. If the food supply crashes, so would the enormous number of passenger pigeons. We think that this resulted in the pigeon numbers undergoing marked fluctuations.”
Flocks of passenger pigeons being hunted, 1875. Image: The Illustrated Shooting and Dramatic News.
There are other, more farfetched theories about the massive population explosion the species enjoyed prior to its extinction. “Some people even say that the astonishing number of the passenger pigeon in 1800s might result from the fact that European settlers wiped out Native Americans, who are the main predator and competitor to the passenger pigeon,” speculated Hung. “Our data, however, is unable to test the hypothesis.”
Unluckily for the pigeons, the boom was followed by a century of these natural and manmade forces working in tandem against them. Martha has become a powerful symbol of that final, dizzying bust, and what it says about a broader problem of human expansion. But as it turns out, she may not yet be the last passenger pigeon ever to take to the skies.
Resurrecting the passenger pigeon is one of the flagship goals of the non-profit genetic research group Revive & Restore. The idea is to extract genes from Martha and her kin, and scaffold them together with those of the band-tail pigeon, Jurassic Park-style.
While these attempts raise a host of ethical and practical quagmires, Revive & Restore argues that the limits of “de-extinction” must be evaluated by geneticists, ethicists, and other experts before the technology becomes widely available.
“Genetic technology is moving so rapidly that amateurs may be able to revive extinct genelines within decades,” says the Revive & Restore project. “It would be preferable to have a full set of publicly understood norms for proceeding responsibly in place by that time.”
Whether or not there are Franken-pigeons in our future, it's worth ruminating on the centennial of this species' extinction. The efforts to save North American birds like the whooping crane or the condor are a great reminder that it's simpler to conserve a species than to have to resurrect it from the dead.