I recently watched the BBC series "Planet Earth," which covers all areas of the world, exploring wildlife, habitats and conservation efforts faced by climate change and the growing human population. I was reminded of the line in one of my favorite Star Trek movies, "The Voyage Home," where the explorers wind up in 1980's San Fransico to track down Humpback Whales, which are extinct by the 23rd Century. In the movie Spock says, "to hunt a species to extinction is not logical."
It also brought to mind another extinct species.
The very last passenger pigeon on earth was a female named Martha who lived at the Cincinnati Zoo. She was born sometime in 1895 or 1897, or perhaps 1900 or 1902, maybe at the zoo or maybe one state over, in Illinois; over the years, many different versions of her story have been offered.
Like all passenger pigeons, Martha was a slim, elegant bird, with long tapering tail feathers and a narrow black bill - a far cry from the crumb-fed rock pigeons of urban America. Just a few decades before her birth, Martha’s was the most common bird species in North America, with individual flocks containing up to or even beyond a billion members.
Martha became the last of her kind upon the death of her companion, George, who also lived at the Cincinnati Zoo. The two occupied a 120-square-foot cage and were fed on cracked corn, wheat, and cooked liver. Whether or not they ever mated is unknown; like the Washingtons, they remained without issue. After George passed away, in July 1910, officials at the Bronx Zoo tried to convince officials at the Cincinnati Zoo to send Martha to New York. They refused.
Martha lingered on in Cincinnati, growing weaker at the same time that she grew more famous.
On August 29, or possibly September 1, 1914, Martha died, and her remains were shipped to the Smithsonian. Joel Greenberg, a Chicago-area naturalist, has written a new account of the passenger pigeon’s demise, A Feathered River Across the Sky. It is a story of unremitting, wanton, continental-scale destruction: in a matter of about four decades, the billion-member flocks were reduced to George and Martha. By the time anyone bothered to try to protect the passenger pigeon, there were too few members of the species left for protection to make any difference. This is obviously a cautionary tale, though one whose lessons, it seems, can easily be misinterpreted.
Some sense of what it was like to watch a flock of passenger pigeons pass overhead comes from the accounts of America’s early colonists. William Strachey, an English gentleman, was sailing to Virginia on board the Sea Venture when it foundered off Bermuda in 1609. When he finally made it to the colony, he described thousands of pigeons filling the sky. In 1631, Thomas Dudley, of Salem, Massachusetts, wrote of pigeons flying overhead in such numbers “that they obscured the light." When the first Europeans arrived in North America, at least one out of every four birds on the continent was a passenger pigeon, and perhaps as many as four out of 10.
Carl Linneaus originally placed the passenger pigeon in the genus Columba, along with rock pigeons, and called the bird Columba migratoria. The species was later moved to its own genus, Ectopistes - from the Greek for “wandering”- and became known as Ectopistes migratorius. Like most migratory birds, they flew south for the winter and north for the summer, but their travels were often unpredictable.
Of course, what looked to humans like motiveless wandering looked very different to the animals involved. The birds’ movements were dictated by want. The prodigious flocks required prodigious amounts of food, which they found in the nuts of trees like beeches and oaks. Beeches and oaks produce big crops of nuts, only irregularly, so the foraging flocks had to hopscotch across the countryside to find enough to eat. When a flock came across a favorable spot and settled down, the weight of so many roosting pigeons could topple trees.
Passenger pigeons remained spectacularly abundant well into the 19th century. John James Audubon was riding through western Kentucky in the autumn of 1813 when he encountered a migrating flock. The birds were still flying when he stopped for the night, and they continued streaming overhead for three days solid. Audubon calculated the size of that flock at 1.1 billion, probably a reasonable estimate.
Over the next few decades, the new nation industrialized, which was good for commerce and bad for the birds. A growing network of railroads meant that even pigeons from relatively remote areas could be profitably transported to big city markets. And with the increasing profits came increasingly elaborate forms of slaughter. Huge net traps were strung across the forests. To attract flocks, the netters would keep some birds alive to use as bait - hence the term “stool pigeon.
Telegraph lines were often laid alongside railroad tracks, and these turned out, as far as the birds were concerned, to have a similarly baleful effect. Rapid interstate communication transformed what had been a local and, owing to the pigeon’s unpredictable movements, haphazard enterprise into a much more efficient, data-driven industry. In 1878, there were still enough passenger pigeons to form a nesting colony that stretched over the better part of three northern Michigan counties.
By the mid-1890s, the only reported sightings of passenger pigeons were of straggly groups that numbered at most in the dozens. There were still pigeons left in the wild until 1902. In 1907, Theodore Roosevelt, then president, claimed to have seen a group at his retreat in central Virginia.
The extinction of the passenger pigeon was an event witnessed, in a manner of speaking, by millions of people. And yet it remains a puzzle. Clearly a species that is routinely being slaughtered as it tries to reproduce is a species that is going to have trouble maintaining its numbers. But many have argued that hunting by itself is insufficient to explain the bird’s total loss. The reasons for this have to do with the same dynamics that drove the slaughter in the first place.
In huge, roosting flocks, the passenger pigeon was easy pickings. As its numbers fell and the great sky-darkening masses dwindled to groups of a few dozen, presumably pigeons became more difficult to find. At that point, the species should have been no more susceptible to hunting than any other medium-sized bird.
In the century since Martha’s death, many additional factors have been proposed to solve this puzzle. One theory as to why scarcity did not save the passenger pigeon is that scarcity itself was the problem.
A variation on this hypothesis holds that the passenger pigeon, which laid just one egg a year, depended on large numbers to satisfy its predators. Its nests were readily accessible to animals like foxes and raccoons.
Yet another theory holds that the additional factor was deforestation. The passenger pigeon population seems to have collapsed in the 1880s, which, not coincidentally was right around the time that land clearing in the eastern United States reached its maximum extent.
Perhaps, in ethical terms, it does not much matter whether overhunting was or was not the sole cause of the passenger pigeon’s extinction. Practically speaking, though, it matters a good deal. At the start of A Feathered River Across the Sky, Greenberg writes that his goal is to inform the public “about the passenger pigeon story and to use that story as a portal into consideration of current issues related to extinction, sustainability, and the relationship between people and nature.” But does not the relevance of this story depend on why the passenger pigeon disappeared?
More than once Greenberg asserts that the passenger pigeon was a victim of bad timing. If even a small population had survived just a few more decades, the species might well have been saved by new laws and attitudes. President Roosevelt established the first national wildlife refuge in 1903, and a decade later, in 1913, Congress approved the Weeks-McLean Act, which gave the federal government power to regulate the taking of migratory birds.
If the passenger pigeon is the icon of an animal driven to extinction through deliberate, wanton, and direct human actions, the continued existence of other species proves that these new conservation measures were effective. Take, for example, the trumpeter swan, which in the early part of the 20th century came perilously close to being wiped out, but which, owing to a combination of stringent protections and reintroductions, has since been growing more numerous. Later, Rachel Carson, in Silent Spring, documented that pesticides were killing a lot more than just pests.
The moral Greenberg seems to want to extract from the passenger pigeon’s story is that conservation measures can work. This is a useful and important moral, but it is not clear that it is the right moral. If the pigeon required great, light-obscuring flocks to successfully reproduce, then probably as soon as the first Europeans appeared and certainly by the time the transcontinental railroad was completed, the species was already doomed. It would not have mattered whether a few stragglers managed to hold on until new laws and attitudes came into play, because the bird needed high densities to survive. Similarly, if deforestation was a major contributing factor, then nothing short of altering the trajectory of American settlement would have sufficed. Perhaps Greenberg is right when he suggests that a serious breeding effort could have prevented Martha from becoming “the last of her species.” But even if a captive breeding program might technically have saved the passenger pigeon from extinction, in any sense that really matters, the bird would still be gone - missing from the forests.
Meanwhile, what goes for the passenger pigeon goes for the long and ever-growing list of endangered species. It is nice to think that once a new problem is recognized, we can address it by enacting or toughening some law. But this kind of piecemeal approach - legislating against this particular practice, or that one - is inadequate to the problem, and probably has been ever since the Sea Venture was wrecked off Bermuda. Toward the end of A Feathered River Across the Sky, Greenberg runs through a litany of threats to what is still called wildlife, though much of it is not terribly wild anymore: overfishing, global warming, pollution, introduced species. He discusses white-nose syndrome, a fungal disease that is devastating bat populations in the eastern United States. The fungus was probably introduced from Europe, and probably inadvertently, perhaps on some tourist’s shoe.
The “deliberate, wanton, and direct” slaughter that the passenger pigeon was subjected to probably could not happen today. Not only laws but attitudes have changed. However, extinction rates now are higher than they have been at any point since the dinosaurs disappeared. The passenger pigeon is part of a much bigger story, a story only beginning to unfold. In this larger narrative, deliberate destruction counts less than the perfectly ordinary, seemingly benign actions of 7.2 billion people.
When we tell ourselves that since Martha’s death, we have learned to take better care of our fellow creatures, we are, sadly, kidding ourselves.
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