More From Living Bird Living Bird Spring 2010—Table of Contents

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Living Bird Magazine Archives “The pigeon was a biological storm. He was the lightning that played between two opposing potentials of intolerable intensity: the fat of the land and the oxygen of the air. Yearly the feathered tempest roared up, down, and across the continent, sucking up the laden fruits of forest and prairie, burning them in a traveling blast of life. Like any other chain reaction, the pigeon could survive no diminution of his own furious intensity. When the pigeoners subtracted from his numbers, and the pioneers chopped gaps in the continuity of his fuel, his flame guttered out with hardly a sputter or even a wisp of smoke.” — Aldo Leopold The Passenger Pigeon was not just a bird. Calling it a “biological storm,” as Aldo Leopold did, was an understatement; it was more like a series of simultaneous biological hurricanes, blowing all the time. Though its appearance was unremarkable, rather like a larger and more vividly colored Mourning Dove, it had habits like no other animal we have ever known. At its population’s peak, four to five billion pigeons roared over the forests and prairies of the East and Midwest, a number equal to the entire population of overwintering birds in the United States. A single flock in motion could darken the sky over 180 square miles, and take days to pass. One recorded breeding colony in Wisconsin in 1871 was 125 miles long and between six and eight miles wide. It covered most of the southern two-thirds of Wisconsin! A flock like this could consume an estimated 210 million liters of food a day. Such a biological phenomenon could not have acted in a void. Modern ecological thinking shows us that if you subtract a species that once comprised 40 percent of all the birds in North America, you lose or change more than just a bird. Passenger Pigeons fed on enormous amounts of “mast,” the nuts produced by the then-dominant species of the eastern hardwood forest: white oak, beech, and chestnut. Of these, two are at least mildly in retreat today relative to other species, one seems to have fewer “crops,” and one is ecologically if not genetically extinct. Other species of plants also seem to be affected. Berries from no fewer than 11 families were dispersed by Passenger Pigeons, and some now rarely fall at any distance from their parent plant. The pure physical effect of the flocks would have been like nothing that exists on the planet today, and perhaps since the days of the dinosaurs. The weight of the pigeons and their nests bore down on the forest like a hurricane, breaking limbs and even toppling trees. But no hurricane would also leave inches, even feet, of nitrogen-rich droppings on the forest floor. Contemporary observers said the ground looked “snow-covered” after the pigeons passed. The droppings first killed grasses and understory vegetation, then promoted riotous growth two or three years later. It resembled the destruction left by a herd of bison or a forest fire. Like these phenomena, it was at first destructive but ultimately regenerative—though the species that took advantage of it look to be different from the ones from before—or those today. The Passenger Pigeon has become a conservationist’s green icon, a symbol of the fertility of the pre-Columbian world and our ruining of Eden. We Europeans came to a world of abundance, cut down the trees, decimated the indigenous people, shot the wildlife, and hauled out barrels of salted Passenger Pigeons in railroad cars to the markets of the East. By the 1870s, the birds were in retreat; in 1914, the last pigeon—cutely named “Martha” after George Washington’s wife—died in a zoo in Cincinnati. The Passenger Pigeon’s extinction symbolizes the heedless exploitation of a continent’s riches at the hands of our culture. All of this is true, as far as it goes. But if you begin to consider the conventional narrative, and look at the tale through contemporary scientific eyes, it begins to look curiously thin. In some ways, humans, and natural processes, may actually have “created” the pigeon just as surely as they destroyed it. I first began looking into the importance of this bird during an Internet discussion among some friends, mostly naturalists and biologists, on rare and extinct birds. Someone asked a question about the Passenger Pigeon. I had been reading about Pleistocene extinctions, the coming of humans to the continent, and the effect of fire on landscapes. Suddenly, all of these phenomena began to seem related. Some of the “facts” about the pigeon and about pre-Columbian America in general began to appear very strange. Things contrary to our simple romantic myths began to emerge from the mists.

During the last period of glaciation, cold steppes existed as far south as the latitude of modern Delaware. South of this ecosystem was an extensive band of boreal forest, which also covered the Rockies, and much of the plains south of glacial-edge steppes were forested as well. Piñon-juniper savannah, better watered than today, covered much of the Southwest. Tropical ecosystems in Mexico may have been drier than today, but were in much the same place. Deciduous forest occupied only a fraction of its later space on the continent, mostly in the far south. According to researcher Emily Russell, pollen studies done in Delaware show “assemblages characteristic of tundra.… The persistence of the assemblages for 1,500-2,000 years in late glacial times suggests stable and cold climate during this time of glacial retreat.” So, where on Earth were the pigeons? How did they get started as a phenomenon unlike any seen before or since? Passenger Pigeons must always have been inhabitants of deciduous forest, eating nuts—especially oak and native chestnut—and berries. It seems impossible under early post-glacial conditions for the pigeon to have existed in anything like the numbers it eventually attained. And without its niche and numbers, a Passenger Pigeon is nothing more than a big, nut-eating Mourning Dove. Before humans and after the glaciers, the Passenger Pigeon was probably much like a southeastern version of the Band-tailed Pigeon of the western mountains, which also eats nuts and sometimes gathers in huge flocks but is not a major player, a maker and breaker of systems. It took the retreat of the ice and human burning to produce that phenomenon—and create the pigeon as we knew it. As the glaciers receded, radical changes began taking place. Humans invaded the continent. Whether small bands who hunted and gathered at the sea’s edge on the Pacific Coast came earlier, or whether—even more controversially—some ice-edge hunters hopped over the margins of the retreating sea ice from Europe, the general consensus is that most of the new Americans came from Asia over the Bering Land Bridge. Recent studies by Stuart Fiedel suggest that the people who became Clovis Man may have come down the ice-free corridor that opened along the flank of the Rockies on dogsleds, taking only a few months. And, whether or not you accept the so-called Pleistocene overkill scenario (a meteor strike in northeastern Canada may also have been the culprit), most of the big native mammals—a charismatic megafauna that rivaled or surpassed that of the Serengeti—were gone in less than 1,000 years (incidentally, according to a recent theory, causing their own shift toward deciduous trees). Today’s so-called “American” megafauna—the modern bison, elk, moose, grizzlies, and wolves—are all from the Old World, just like humans. Our only true native large mammals are deer, pronghorn, coyote, and puma. A few of the new creatures had disproportionately large impacts on the ecosystem. Bison of several sorts had already existed in the West, but the new smaller species, perhaps less constrained by competition or encouraged by a warmer climate, helped create a plains ecosystem that lasted until the buffalo hunters and sodbusters destroyed it. Meanwhile, east of the plains, the clever new immigrant from Asia began burning the forest. Most modern ecologists—following the lead of “fire historians” such as Stephen Pyne—now believe that the environment Europeans first saw in North America was largely shaped by humans already, using fire as a tool. The plains advanced in runners that would eventually reach to the East Coast, carrying with it the open-country species such as bison, elk, and prairie grouse. They all ranged as far as what is now Massachusetts in the Northeast, where the last “Heath Hen,” a subspecies of Greater Prairie-Chicken, would perish in the early 1930s.