A Tale of Three Superdoves: the Dodo, the Rock Pigeon, and the Passenger Pigeon

This year marks the centenary of the death of the last Passenger Pigeon, the most numerous bird ever known, but one that did not survive the colonization of North America. I am willing to mourn that last captive voyager, a miracle of evolution, a postcard for extreme biodiversity, a bird more appreciated now than it ever was in life, except as a meal. But first I want to test the sophistication of your biophilia. So, how do you feel about “street” pigeons? Do you mourn the Dodo?

Many people, at least in cities where Rock Pigeons are common, think of them as “flying rats.” When Richard Johnston and Marian Janiga began writing Feral Pigeons, their illuminating and entertaining study of the bird, many academics were horrified—a strong bias still exists against studying domestic or feral animals. That subject is one for agricultural schools. Perhaps the critics have forgotten a guy called Charles Darwin, who, despite his social position as a member of the country gentry, was interested enough to attend pigeon shows, buy birds, and bore dinner guests such as Charles Lyell with his obsessive table talk about them.

Although you will see that the “superdove”—a term coined by David Quammen—is eminently worth studying, I would propose that there are, or were, three peculiar members of the dove family deserving of that title. Two (the Passenger Pigeon and Dodo) are gone; the other (the Rock Pigeon) may never be eradicated. Despite our good or bad intentions, we are a part of a larger system and affect it in surprising ways we do not intend or yet understand. The real story of the superdoves is yet to be written, but we have enough data to realize that every action has consequences, and they are not always the ones that you see coming. The fate of the superdoves is intimately braided with that of our species, and has been for millennia.

The biggest and oddest dove was the Dodo—a huge bird (three feet tall and weighing up to 40 pounds) resembling a giant hatchling found only on the Indian Ocean island of Mauritius, a predator-free Eden. It did not survive its first encounter with our species, killed off with contemptible ease as a healthy food for visiting sailors tired of hardtack and salt beef. The Dodos were gone by 1662, when the notion of extinction didn’t even exist.

The second species, the Passenger Pigeon, was physically unremarkable. Recent genetic evidence suggests it was a normal dove, more or less closely related to the Band-tailed Pigeon of the West. But it was the most numerous bird on earth; at its population’s peak, four to five billion pigeons, a number equal to the current year-round population of all North American birds combined, roamed the nut-rich forests of the East and South. A single flock in motion could darken the sky over 180 square miles. It was said to “migrate,” but it left devastation in its wake, especially on its nesting grounds, where it killed its nesting trees by physically breaking their limbs; the weight of the pigeons smashed the forest like a hurricane. Their droppings killed off grasses and understory vegetation, then rebuilt the pigeon-made wastelands as they aged into fertilizer, or, in the southern part of the range, converted former woodlands into “canebrakes,” impenetrable thickets of bamboo that might be 20 or 30 feet deep, and hosted their own vanished or diminished ecological community.

When you encounter a mounted Passenger Pigeon in a glass museum case, it is always a shock. Preserved, well or badly, it looks like an ordinary little pigeon. It is hard to imagine that, collectively, it was one of those unusual species that shapes its environment—perhaps the most dramatic one encountered by humans anywhere; the only species between the extinction of the sauropod dinosaurs 65 million years ago and our own industrial civilization that could dramatically “restart” its habitat. Not even African elephants or the plains bison came close.

And then the Passenger Pigeon was gone, in a geological instant. Its destruction is a strong contender for our deadliest ecological sin. The Passenger Pigeon is a comfortable martyr: gone, romantic, even mythic. We can mourn its unique lifestyle without having to think about what it would be like to exist with a living hurricane. We know it was killed by our industrial-strength exploitation. A. W. Schorger, its original and most dedicated chronicler, conveyed the conventional wisdom in 1955, and the latest account, Joel Greenberg’s A Feathered River Across the Sky, echoes his harsh accusation: “All thinking people now realize that man alone was responsible for the extinction of the Passenger Pigeon.”

But did we intentionally kill the Passenger Pigeon all by ourselves? We exploited many species—why did only the most abundant species of bird not just die, but die out, as poet James Dickey said in his fierce poem about extinction, “The Last Wolverine”? I believe some intriguing evidence suggests that, even as we were shooting down what seemed to be an inexhaustible bounty of wild pigeons, something else was going on, something we did with the unwitting help of our overlooked congener, the last surviving superdove, the Rock Pigeon.

That is a puzzle I think we may solve in the next few years. But I am intrigued by a bigger and more difficult mystery. The great paleontologist Robert Bakker is known for his impatience with the public’s obsession with the last day and dramatic end of the dinosaurs, and baits his audiences with what he thinks are more important questions: What was their origin? Where did they come from?

So get yourself a map of the ”last glacial maximum” and see where the southern edge of the great glacier stopped before it receded, about 12,000 years ago. A substantial town on the edge of the plains, Kansas City, anchors what might be the glaciers’ southernmost point; the ice runs out to the eastern edge in what is now Delaware. Think about the tundra that grew near the towering face of the ice, and the boreal conifer forest that grew south of that point, and remember the Passenger Pigeon’s dependence on “mast” (nuts). Then tell me: Where was the Passenger Pigeon?

And where was the last remaining superdove? Columba livia, the Linnaean name for the wild Rock Pigeon, comes in three iterations: the blue Rock Pigeon itself, rock-nesting, relatively rare, and possibly declining; the pampered domestic pigeon, cherished and bred from South Africa to China for everything from pigeon shows to long-distance, big-money races, to commercial squabs for sophisticated diners; and the genuine superdove incarnation, the descendant of escaped domestic birds that live like the old ancestral blue Rock Pigeon but close to or among humans, in their biggest cities, or as aliens on other continents. As they settle into these niches, new environmental challenges bring out new characteristics, as Darwinian processes shuffle their genes and deal out infinite untried combinations. Some of these will be adaptive, allowing it to live well in environments that would have killed its predecessors, not least because it has become resistant to pathogens that have whittled away any susceptible ancestors.

This third iteration of the Rock Pigeon is a biological and ecological prodigy, but it gets no respect. We invited it in thousands of years ago, and made many breeds by selecting for various physical and behavioral traits. We killed off the ungainly Dodo and astonishing Passenger Pigeon, but although we try, we can’t rid ourselves of the last superdove; I expect it will be with our species as long as we build structures.

An Icon of Extinction

The Western World stumbled upon the Dodo on a remote island in the first great burst of exploration, when its ships began to circumnavigate the globe and bring back treasures. Though they were not looking for them, some of their most important treasures were living beings, new to their collectors and as odd as creatures from an alien planet.

You can—or could—see a real Dodo today. When I was visiting Jonathan Kingdon in Oxford in the 1990s, he was called away on a rainy day and advised us to go to the Oxford museums. He told us they had an old dead bird that would be of great interest.

Hanging in a glass case on the wall was the undeniable head of a Dodo, charred, broken, and with pieces missing. It still stirred my imagination more than any reconstruction or mounted specimen could have, embodying its own mysterious history as well as that of its own vanished species. It appeared in a catalog of John Tradescant’s museum in London in 1656 as “a dodar from the island of Mauritius.” It was nearly lost in 1755 when the trustees of the museum ordered it to be destroyed because it was half-decayed and lacking in appeal. The head and foot that were snatched from the bonfire are all that remain; all other “stuffed” Dodos are reconstructions using things like goose feathers.

To a naturalist interested in evolution, this Dodo is one of the most important relics in any museum, comparable to Roy Chapman Andrews’ Protoceratops nest, which contains the first dinosaur eggs ever found, restored to the museum in Mongolia, and displayed so children can touch them. I couldn’t touch these Dodo remains, but I must have spent an hour with my nose pressed to the glass.

Two things are obvious to an observant student. One is that nobody has exaggerated the Dodo’s cartoonish head: its face looks just like the pompous figure of John Tenniel’s cane-carrying Dodo illustration in Alice in Wonderland. If you wish to envision a living Dodo, this is important, because although many artists drew and painted the bird from the 1600s through today, few, if any, were drawn from life. When John Tradescant acquired his specimen, the bird was already extinct. Its actual encounters with humans stretched from 1599—when the bird was described by a passenger on a ship that had first arrived at Mauritius in 1598—to 1662, when the last known specimen was eaten.

It might be worth mentioning here that in the 1600s and even 1700s, the entire concept of “extinction” as we understand it did not exist. Its closest approximation was that life was created and destroyed several times; such theories were held into the 19th century by such respectable scholars as Georges Cuvier and Louis Agassiz. Influenced in part by a literal reading of the Bible, many philosophers believed that all species had been created in their special niches and would last there through their epoch at the very least. This is why even the relatively secular Thomas Jefferson asked Lewis and Clark to keep an eye out for mastodons. And why, as late as the 1890s, many laymen still believed that the Passenger Pigeon had flown to Siberia, Greenland, or the moon rather than actually disappeared.

The other odd thing I saw in the Oxford head might only be noticed by a pigeon fancier (I wonder if Darwin, who was one, ever thought about it?). A Dodo resembles nothing more closely than a 10-day-old chick or “squab” of the common Rock Pigeon. The idea of neoteny, the retention of embryonic or juvenile characteristics until maturity, is often mentioned in describing such animals as the domestic dog compared with the wolf, but it is most obvious in the Dodo. Our Oxford host, Jonathan Kingdon, the unique polymath, artist, and zoologist whose myriad books and original sculptures illuminate evolution more vividly than any other contemporary works, agreed. His son Rungwe, who runs Pangolin Editions, the biggest sculpture foundry in Europe, later collaborated with his father to create bronze sculptures of Dodos as part of a series promoting conservation in Mauritius. Rungwe’s drawings of pigeon nestlings and Kingdon’s bronzes, now displayed on the island, illustrate the phenomenon better than my words can.

The exaggerated features of the Dodo result from its retention of juvenile characteristics into adulthood. Perhaps it evolved into a giant chick simply because it could do so in the absence of predators; more probably, because it gained some advantage, such as being able to process enormous amounts of food in a short time. But the effect was to make the bird resemble a cartoon—a cartoon so recognizable that Dodos figure in everything from Alice in Wonderland to modern advertising. But if it was a cartoon, it was evolution’s cartoon.

The great bird anatomist Katrina van Grouw wrote me when I began thinking of this essay and said, not entirely in jest, “Between you and me, I think these flightless island species quite pathetic. Quick enough to chuck flight out the window as soon as they get the ‘all clear,’ and then they blame everyone else when they go extinct.” The grain of truth in her wisecrack has been documented by ornithologist Jared Diamond. Species extinction has always been associated with islands. But attributing such human traits as stupidity and laziness to island endemics is a little too simple. To be alert, to be ready to flee or fight, requires a lot of calories, a lot of food. In the absence of any predators it makes perfect energetic and ecological sense to lose these abilities; the advantage of losing energy-hungry organs or habits is often underestimated. David Quammen’s “ecologically naïve” is more nuanced.

The trouble for these species comes when the islands are invaded by predators. Most of these islands were inviolate sanctuaries before modern humans erupted in an advancing wave out of Africa. The late Paul Martin was the one who put together the Pleistocene Overkill hypothesis, now accepted by most paleontologists with a few caveats. The idea is that the large mammal and bird fauna disappeared as the bands of clever hunters from Africa appeared, with almost eerie precision—not so much in Africa, where modern humans evolved alongside their charismatic neighbors such as elephant and lion, but in the Mediterranean, Europe, and all of Eurasia. They moved quickly along the littoral all the way to Australia, where fires blossomed and dread monsters such as the marsupial lion and the giant monitor lizard followed their prey into oblivion, continuing throughout the islands of the Pacific, arcing across the Bering Strait, down the coast all the way to South America, and also down the slender “ice-free corridor” onto the North American plains, killing mammoth and bison, firing and changing the forest into a more productive form, and finally occupying the islands of the Caribbean and cleansing them of such marvels as a giant flightless Bahamian Barn Owl. We were left with the diminished fauna and flora we call “wild” today. As Australian conservationist Tim Flannery says, the great charismatic Pleistocene megafauna vanished down a Black Hole—that hole being the ever-hungry and never-too-discriminating mouths of our ancestors.

The Dodo probably had no chance against the Black Hole. It was flightless, slow, “naïve,” and supposedly tasted good to humans. The thing that strikes me after reading two recent books on the species, two more on extinct birds, and one on pigeons—not to mention the scientific papers—is that we know nothing about the Dodo. Julian Hume and Michael Walters’ Extinct Birds says it outright: “In reality, virtually nothing is known about its life.” We think we know what the Dodo looked like, but few or none were painted from life in the West, as can be attested to by their lumpiness and carefully copied mistakes. My best candidate for a live portrait is a Mogul miniature, dated 1625 and kept at the Institute of Oriental Studies in St. Petersburg, Russia: “Birds in the menagerie of Jahangir.” The parrot, pygmy geese, sandgrouse, and displaying tragopan are realistic; why not also believe in the accuracy of the artist’s dark, slender, lively Dodo?

Early Arab chroniclers of voyages to Mauritius never mentioned the bird, but before we bemoan their lack of curiosity we should remember that our best specimen was thrown away, under orders, and rescued from a bonfire. We know that it was rare, and “To be rare is to have a lower threshold of collective catastrophe,” writes David Quammen. And we know that it is gone.

A Living Storm

If data imply knowledge, we know a lot more about the Passenger Pigeon than we ever will about the Dodo. The first vivid account of the creature that Aldo Leopold called “a feathered tempest” was French explorer Jacques Cartier’s in 1534, when he saw a typical “storm” of the birds on Prince Edward Island, off the northeast coast of North America. But from the 1700s all the way to the bird’s sudden dwindling and disappearance ending with the death of Martha in 1914, a chronicler had more of a problem deciding which texts to use than finding sufficient material. Two well researched books cover the bird’s sad story, The Passenger Pigeon: its Natural History and Extinction, by A. W. Schorger in 1955, and the new A Feathered River Across the Sky, by Joel Greenberg. Both chronicle the Passenger Pigeon’s incredible numbers, unknown in any other land vertebrate in human history, and quote from contemporary accounts that read like a cross between Hieronymus Bosch and Cormac McCarthy. Greenberg vividly chronicles the slightly deranged attitudes of some pigeon killers, who seemed to go into reflexive killing loops like predatory animals on autopilot—weasels in henhouses, wolves in a herd of sheep—killing again and again in a mindless frenzy: “‘Bite their heads! Bite their heads!’ I replied…‘Not for all the pigeons in the world’… I could kill pigeons with a gun without any compunction. But crushing the skulls of live birds between my teeth! Faugh!”

Despite the color he adds, Greenberg comes to the same conclusion: we killed them as thoughtlessly as we did the Dodo: “Man alone was responsible.” A fair indictment, perhaps, and certainly one that we deserve for what we have done to other species—the Dodo was eaten up by the Black Hole as casually as a snack, for its ease in harvesting. But I see a few things that do not make sense in the simple “heroes and villains” version of the pigeon’s fate. I have written on the species for Living Bird (“A Feathered Tempest,” Spring 2010), and I have no desire to go over the same ground, but a few points I made and questions I asked there have not gone away.

First of course, what, and where, were they at the last glacial maximum? Second, what did they do as a species between the end of the ice and the coming of humans, in the form of Clovis Man, down the interglacial corridor 12,000 years ago? The Passenger Pigeon’s origin bears on its fate.

What was the composition of the forest east of the Mississippi then? How did it change until 1492? Why did it change? How did human burning affect mast species? How extensive was it, when did it start, and how much did it change and influence that composition? Was burning so extensive that the so-called wilderness that greeted Europeans was really a kind of garden, as much a human construction as a cathedral, as one can take from books by Stephen Pyne (Fire in America) and Charles Mann (1491)? Or is this just a piece of romantic overcompensation, as suggested in a recent paper, “Indian Fire Use: Deflating the Legend,” by Stephen W. Barrett, Thomas W. Swetnam, and William L. Baker? What other causes may have affected the specific flora there?

A simpler question, with implications: did the Passenger Pigeon migrate, with a “home” at each end like a conventional bird, or did it wander? This may bear upon a great and unnoticed archaeological mystery: a search of all sources of pigeon-eating and bones, through all of pre-Columbian time, has yielded very few remains, at only two sites, of what was the most abundant species of North American bird ever to exist—less than the weight of protein at a single serious buffalo jump.

These questions are a long way from being answered. One thing that they strongly suggest is that the Passenger Pigeon as an almost geological force on the landscape is probably a postglacial phenomenon. The most intriguing implication is that it might also be a partially human-conditioned phenomenon, created by humans burning the eastern deciduous forest, or at least that both Native Americans and Passenger Pigeons both had a part in creating that intricate landscape of forest and savannah. Greenberg comes very close when he writes, “The most profound alterations brought about through pigeon-generated damage were an increase in the frequency and intensity of fires.” He sees the correlation but not the result. (Charles Mann’s theory that the pigeon’s numbers increased suddenly after fast-running pathogens killed off the Native American population ahead of the European invasion is intriguing, but he allows far too little time for the increase, even if Indian predation had been suppressing the numbers of the bird.)

The other part of the pigeon myth that doesn’t quite work is the shape and sudden rapidity of its final extermination. Recent theories about the breaking up of the mast forests add to the picture, though small groups could still nest successfully; the pigeons mated and raised young in aviaries in America and Europe. My suspicion is that a slowmoving pathogen that affected reproduction might have combined with mass killing and habitat destruction in a one-two-three punch that could do what no amount of deliberate human Columbicide could do. In an ironic twist, the carrier of such a pathogen could well have been their semidomestic relative, the Rock Pigeon, brought into close proximity to the Passenger Pigeons by European colonists. Records show that Passenger Pigeons and feral Rock Pigeons watered together at farm ponds after the cutting of the forests. The modified superdove survives and carries diseases that would have easily overwhelmed more innocent immune systems, as ours did to the native tribes.

Superdove

Earlier I asked if you like street pigeons. Inhabitants of our modern cities dislike Columba livia; country dwellers, pigeon eaters, and fanciers love the bird, and brought it with them to every continent. The domestic pigeon was an example for Charles Darwin and an early long-distance communication system for civilizations stretching from Western Europe to Central Asia. The original Rock Pigeon was versatile enough and historically had a range covering much of northern Eurasia. Human selection’s products emphasizing one set of genes or another were a less versatile shuffling of the deck. But when a random assortment of those exaggerated birds went back to the wild, what survived was still another reshuffling, this one accomplished through natural selection. The result is the bird whose chroniclers, Johnston and Janiga, write of under the name of “feral” pigeon. Though superficially resembling its ancestors of cliff and pigeon loft, it is stronger and more adaptable than any bird of its kind. Quammen summed up its abilities in straightforward language: “They fly faster. They eat a more diverse diet. They breed earlier in life, more abundantly throughout it, and repeatedly during the course of a year. They travel long distances, transplanting themselves into new terrain with the robust impertinence of weeds. They have invaded the concrete environments that the human species constructs for itself. They succeed in living at high population densities in close proximity to people who despise them. They can hear high-frequency sound; they can see ultraviolet.” Johnston and Janiga add, “Feral pigeons are something special, different in important ways from wild Rock Pigeons as well as from domestics.”

So I give you the monster pigeons, our congeners, the superdoves: three species whose stories illustrate how other lives are now inextricably entangled with ours. Humans eliminated the biggest pigeon that ever lived, with shameful ease; helped, perhaps, to create, then exterminate, the world’s most abundant bird, partly by accident; and, at the same time, were inadvertently causing an already successful pigeon to expand and evolve further in multiple habitats, so that although we deliberately try to eliminate it from our cities, we are unlikely to do anything but spur its further evolution. Our myths and our preconceptions about animals are often built on vapor. It could well be, to paraphrase the words of the old Firesign Theater troupe, that everything you know about Passenger Pigeons, and the familiar street pigeon beneath your window, is wrong.