The Condor's Shadow: The Loss and Recovery of Wildlife in Americaby David S. Wilcove
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The vast majority of American forests, prairies, and rivers have been logged, plowed, dammed, and developed. Hundreds of species have vanished completely and many others are now in danger. And yet, in some areas there are more acres of forests now than at the turn of the century and many of our lakes and rivers are cleaner today than they were twenty years ago. What exactly is the state of wildlife in America today?
Second Nature attempts to make sense of these complex, and often contradictory, patterns of change. A comprehensive overview of where we stand today ecologically and how we got there, it describes how nature has responded to the ruinous forces human beings have unleashed upon it habitat destruction, air and water pollution, overkill, and the introduction of exotic animals and the diseases they carry. By exploring the cycles of loss and recovery that have characterized many ecosystems during the last fifty years, David Wilcove a senior ecologist at the Environmental Defense Fund presents a compelling ecological history of American wildlife.
A unique synthesis of the many diverse elements that make up our ecological landscape, Second Nature is essential reading for anyone interested in saving what is left of our natural heritage.
"This engaging report, sprinkled with sensible, targeted solutions to specific problems, is essential reading for concerned nature lovers, as well as a basic resource for environmentalists and policy makers."Publishers Weekly (starred review)
"Every bit as wise as it is readable. For a general reader, it is an unalloyed delight; for a conservationist, it is nothing less than essential."T. H. Watkins
"Wilcove's fine contribution gives important support to the argument for a new and enlightened American ethic." E.O. Wilson
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I live on the outskirts of Washington, D.C. From time to time, a business meeting or ballgame requires me to travel to Baltimore, a distance of approximately 40 miles as the crow flies. My route takes me through the center of Washington and then in an easterly direction along the Baltimore-Washington Parkway. Sealed inside my automobile, I have plenty of time to ponder how the landscape around me has changed since the arrival of European settlers.
Let us imagine this same journey taken in three different years in May: in 1498, 1898, and 1998. What we see and hear will be typical of what is happening in much of the eastern United States, although the particular species and the timing of events may differ.
Traveling between the two nonexistent cities in 1498 amounts to a major expedition, for we must proceed on foot, taking advantage of whatever game trails or Indian pathways we find. For most of the journey we travel within a magnificent old-growth forest. Oaks, chestnuts, and beeches tower above us. Beneath them are two or three layers of smaller trees, while jack-in-the-pulpits, mayapples, and other wildflowers cover large portions of the forest floor. The songs of red-eyed vireos, black-and-white warblers, scarlet tanagers, and other songbirds fill the morning air, but the birds themselves are surprisingly difficult to spot in the tall trees. In wet mud along the Patuxent River floodplain (marking roughly the halfway point in our journey), we find the tracks of a mountain lion, as close as we shall cometo spotting the elusive cat. Proceeding farther, we startle a herd of elk, glimpsing a dozen tawny rumps as they disappear within the forest. Had we begun our trip in January instead of May, we might well have encountered bison, but they have since moved north, where they will remain until the snow once again brings them back to our area.
It is now 1898, and our trip will require the better part of a day with horse and carriage. In downtown Washington (a city of approximately 278,000 people), we spot flocks of house sparrows and pigeons searching for food in the muddy streets. The sparrows are the descendants of birds that were brought from Europe and released in the city in 1871. The pigeons date back to the colonial era, when they were carried across the Atlantic to serve as food and pets. Because we are proceeding at a leisurely pace, we are able to spot robins, blue jays, and cardinals in backyards and tree-lined streets; unlike the sparrows and pigeons, these birds are native to this region. Exiting the city, we pass through miles and miles of farm fields and hedges. Meadowlarks are stationed every few hundred yards along the fence posts, staking out their territories with loud, sweet whistles. Bobolinks hover above, singing their ecstatic trills and buzzes, while bobwhite quail call from the edge of a nearby woodlot. With more time we might explore the woodlots scattered among the fields; if we did, we would surely encounter some vireos, warblers, and tanagers, much as we did in 1498. But by and large we are in farmland, not forest, and the land belongs to the meadowlarks, not the tanagers.
The most recent trip is, of course, the easiest one, just an hour's drive if the traffic is light. As we pass through Washington (now a city of over half a million people), pigeons peer down at us from monuments, rooftops, and overpasses. House sparrows and starlings squabble over scraps of food around a garbage can. The starlings, which were not around at the turn of the century, are descendants of a flock of sixty brought from Europe in 1890 and released in New York City's Central Park; their progeny subsequently spread across the entire continent. Upon entering the Baltimore-Washington Parkway, we begin to tally the dead mammals along the roadside (the live ones being far too elusive to spot from a car). We record raccoons, opossums, skunks, and the occasional dog or cat. Approaching the forests lining the Patuxent River, we pull over, exit the car, and begin walking into the woods until the din of the highway has largely vanished. All around us red-eyed vireos are singing, and we quickly pick out the songs of a black-and-white warbler and a scarlet tanagerprecisely the species that greeted us at this very spot half a millennium earlier. Wanting to see the brilliant red and black hues of the tanager, we hike farther, but succeed instead in spooking a white-tailed deer and a gray squirrel. With time running out, we return to the car and continue the drive, arriving in Baltimore in time for breakfast. Stopping at a fast food restaurant, we are greeted by another contingent of starlings and house sparrows, fighting over scraps.
Our time travels have highlighted a cycle of profound ecological importance: the destruction and subsequent regeneration of the forests of eastern North America. So thorough were the settlers and timber companies that, over the course of about two centuries, almost every acre of virgin forest from Maine south to Florida and west to the Great Plains fell to the ax or saw. The cutting began along the eastern seaboard, spread to the Ohio Valley and the Midwest around the time of the Civil War, and moved north to the upper Great Lakes at the close of the nineteenth century. "The pattern of the spread of lumbering ... was one of a continuously expanding wave of exploitation, which, despite local pauses and advances, moved with generally gathering momentum westward across the continent, with an important projection that swept down through the South." Today, less than 2 percent of the virgin forest of the eastern United States still stands, a bleak tribute to the insatiable hunger for farmland and timber that characterized the settling of the East.
The cutting of the virgin forests coincided with an era of unregulated hunting and trapping that reached its peak in the latter half of the nineteenth century. The breadth and magnitude of this overexploitation are difficult to overstate, especially in comparison with today's stringent bag limits and seasonal restrictions on hunting. Overexploitation equaled or exceeded deforestation as a factor in the disappearance of mammals and birds from the eastern forests. Together, the one-two punch of deforestation and overhunting eliminated virtually all of the large predators and hoofed mammals in the East. Well over a century later, the ecological consequences of their elimination are still unfolding before our eyes, as populations of other plants and animals increase or decrease in response.
In only a handful of places, such as Minnesota's Boundary Waters and the southern Appalachians, do sizable tracts of virgin forest remain, places where a person can hike among the big trees for several hours and feel as though he has stepped into the boots of pioneer naturalists Mark Catesby or John James Audubon. Elsewhere, ecologists search diligently for every remaining acre of primary forest, and the discovery of even the tiniest scrap is deemed worthy of celebration. None of these primeval forests, not even the largest tracts, contains the full array of species that greeted the first European settlers.
What were these original forests like? It is tempting to portray the precolonial landscape of the eastern United States as an unbroken blanket of primeval forest, a green wilderness where a squirrel could scamper from the Atlantic Ocean to the Mississippi River without ever touching the ground. However appealing this image might be, it is also inaccurate. Natural disturbances such as fires, windstorms, and insect outbreaks, combined with fires and clearings perpetuated by American Indians, assured that the "blanket" was, in fact, something of a patchwork quilt, consisting of forest patches of different ages and sizes. From Massachusetts southward, most tribes had strong agricultural traditions, clearing the forests around their settlements to plant maize, potatoes, squash, sunflowers, beans, tobacco, and other crops. As the fertility of the soil diminished and crop yields fell, as the supply of fuelwood surrounding their villages was exhausted, as populations of game animals declined, or as the volume of refuse reached intolerable proportions, the tribes would abandon their fields, allowing the forests to regenerate. This "slash-and-burn" method of farming would be replaced with more efficient but less sustainable modes of exploitation when the European settlers arrived. In addition, many tribes burned the forests in the spring and fall to create better habitat for deer, quail, and other game animals and to maintain grasslands and clearings.
Estimates of the precolonial population of the United States and Canada range over an order of magnitude, from one to twelve million. By any estimate it was a substantial number, capable of altering the vegetation over much of the East. The accounts of early European settlers describe large areas devoid of trees and forests so open that one could gallop horses through them. Describing the landscape around Salem, Massachusetts, in 1630, one colonist wrote: "[T]here is much ground cleared by the Indians ... and I am told that about three miles from us a man may stand on a little hilly place and see diverse thousands of acres of ground as good as need to be, and not a Tree on the same." Adding to the mosaic-like quality of landscape was the natural diversity of the plants themselves. Historian William Cronon relates the experience of explorer James Rosier, who, while ascending a river in Maine in 1605, encountered great, old oaks growing in open fields, dense thickets of shrubs and saplings, and conifers so tall they were fit to serve as "masts for ships of 400 tun," all in the space of 4 miles.
Although the virgin forests were never as vast as sometimes imagined, and while the Indians altered the face of the land more extensively than previously thought, there seems little doubt that on the whole the precolonial forests were grander and more extensive than anything we enjoy today. Colonist after colonist wrote home to England to gloat about the magnificent trees that were so abundant in the new land. Today, we live surrounded by woods that bear little resemblance to the forests that greeted those first settlers. "Our whole concept of a healthy and mature forest now applies to something that once would have been considered inferior and scraggly." We will never know the full impact of the deforestation of eastern North America on its wildlife. The effects of deforestation are difficult to disentangle from the effects of overhunting, the accounts of early naturalists are woefully inadequate for unraveling such a complex puzzle, and many of the clues disappeared with the great trees. But we can be certain that the impact was enormous.
While it is now difficult even to imagine a bison, gray wolf, or mountain lion roaming the forests of New Jersey, Delaware, or Maryland, at one time these species were an integral part of the fauna of eastern North America. In the Northeast, they were joined by caribou and moose. Exactly how common these species once were will never be known, but one can gain some appreciation for their former numbers by examining old hunting records. In 1760, for example, north of Harrisburg, Pennsylvania, two hundred settlers encircled an area of approximately 700 square miles and slowly marched inward, shooting any animal they saw. Their goal was to rid the area of the mountain lions and wolves that "had been troubling the more timid of the settlers," but their blood lust extended well beyond those two species. By the end of the hunt, the settlers had killed "41 panthers [mountain lions], 109 wolves, 112 foxes, 114 mountain cats [bobcats], 17 black bears, 1 white bear, 2 elk, 198 deer, 111 buffaloes, 3 fishers, 1 otter, 12 gluttons [wolverines], 3 beavers and upwards of 500 smaller animals." The numbers of wolves and mountain lions in particular are surprisingly high even for an area of that size, casting some doubt on the accuracy of the count. But the fact that there were significant numbers of large predators and ungulates (hoofed mammals) in the eastern forests in the colonial era seems indisputable.
A population that values domestic livestock, avidly consumes wild game, and has little knowledge of ecology is likely to show little tolerance for wild predators. The settling of the East, therefore, was marked by a concerted effort to eliminate its wolves and mountain lions. By the mid-1600s, New England colonists were already complaining about livestock depredation by gray wolves, and they employed bounties, poisons, and special hunters to get rid of them. Wolves were extirpated from New England by the 1860s, and from New York and Pennsylvania by the start of the twentieth century. Farther south, they held on a little longer in the Appalachian Mountains, but vanished in the beginning decades of the twentieth century. Today, in the eastern United States, gray wolves survive only in the northern Great Lakes region.
A second species of wolf, intermediate in size between the gray wolf and coyote, once occurred in the swamps and forests of the southeastern United States, from North Carolina south to Florida and west to Texas, Oklahoma, Arkansas, and Missouri. The red wolf does not hunt in big packs or kill large livestock (although poultry and newborn calves are occasionally taken). Indeed, this timid animal hardly posed an economic or physical threat to the farmers who killed it. Although the red wolf managed to persist in the East far longer than the gray wolf, by the late 1960s it had been reduced to a single population living in eastern Texas, a population that was in imminent danger of genetic disintegration because the wolves were hybridizing with coyotes. In the mid-1970s, the U.S. Fish and Wildlife Service staged a Dunkirk-like rescue of the red wolf, bringing as many of the wild animals as possible into captivity. Of the four hundred canines captured by the Service, only forty were judged to be "pure" enough red wolves to use in a captive breeding program. The program worked well, enabling the Service to move on to a much tougher challenge: reintroducing red wolves into the wild. In 1987, the Service began releasing animals in the Alligator River National Wildlife Refuge and nearby Pocosin Lakes National Wildlife Refuge in coastal North Carolina. This effort has, predictably enough, encountered pockets of local resistance, but far less opposition than one might have expected, given the troubled history of people and wolves.
The mountain lion, too, was eradicated from virtually its entire range in the East, but due to its extraordinarily elusive nature, the precise dates of its demise are impossible to determine. The last bounty in Connecticut was paid in 1769, while in Vermont and New Hampshire lions persisted for about a century longer. In New York, they survived in the Adirondack Mountains until the very beginning of the twentieth century. The southern Appalachians became one of the last refuges for eastern mountain lions, where they were reliably recorded until the 1930s. In the more remote and mountainous regions of Virginia, Tennessee, and North Carolina, sightings of mountain lions are still reported from time to time, but one should probably assume they represent either escaped "pets" or misidentifications, rather than miraculous survivors of centuries of persecution. Occasional sightings in New England may represent escaped captives or possibly wandering individuals from the wilder parts of Canada. Remarkably, a tiny population of about thirty to fifty mountain lions still survives in the Everglades, but it seems only a matter of time until a combination of natural mortality and pressure from Florida's ever-growing human population snuffs out this ember of eastern wildness.
The elimination of big predators from nearly all of the eastern United States was an ecological experiment of enormous proportions, an experiment conducted long before there were ecologists to deduce its results. To guess at the consequences, therefore, one must turn to recent ecological studies from a variety of locales. A growing number of biologists believe that top predators play a critical role in maintaining the diversity of species within natural communities. In tropical forests, for example, jaguars, mountain lions, and ocelots are thought to depress populations of their prey species, which include various seed-eating rodents and omnivorous mammals such as the coatimundi, a tropical relative of the raccoon. In places where the cats have been shot out, which means almost any forest accessible to people with guns, these prey species are an order of magnitude more abundant. If populations of seed-eating mammals increase in numbers because they have fewer predators, they can suppress the regeneration of various trees by consuming large numbers of seeds. Tree species diversity can thus be reduced, causing the loss of additional species that depend upon certain types of trees. Furthermore, omnivorous mammals such as coatimundis consume the eggs and young of ground-nesting birds. As their numbers increase in the absence of big cats, they can drive ground-nesting birds to extinction.
As we shall see, both these phenomenaa reduction in plant diversity and the disappearance of ground-nesting birdsare occurring today in the eastern United States, and the historic loss of top predators is a principal cause. However, I suspect few such effects would have been apparent in the nineteenth or early twentieth centuries. The settlers were hell-bent on killing both predators and prey. Populations of bison, elk, caribou, deer, and even raccoons could not have responded to the absence of predators at that time because they too were being ruthlessly exploited.
The bison were the first to go. Although most people today think of them as animals of the Great Plains, at one time bison ranged as far east as Pennsylvania, New York, and perhaps New England, and south to Florida. The last bison east of the Appalachians was killed at the appropriately named Buffalo Cross Roads, near Lewisburg, Pennsylvania, in 1801, and the last individuals east of the Mississippi were a cow and her calf taken in West Virginia in 1825. Elk persisted somewhat longer, retreating as did the bison and mountain lions into the Appalachian wilderness. The last native elk in Virginia and Pennsylvania were shot in 1855 and 1867, respectively. Caribou, now usually regarded as denizens of the tundra, once occurred as far south as the northern Great Lakes and Maine. Gone from Maine by 1908, they held on in the Great Lakes region until the 1940s.
Even the white-tailed deer, so common today, was once nearly extirpated from the East due to unregulated hunting. Like the other large ungulates of the East, they experienced a tremendous population decline in the first two centuries of European settlement, when predation by a rapidly growing human population more than compensated for the absence of wolves and mountain lions. By the end of the eighteenth century they had vanished from large portions of New England, and they were so scarce in Maryland at the turn of the twentieth century that some naturalists thought them locally extinct. As late as 1950, one Maryland naturalist would write:
In a number of other ways this large mammal has difficulty adjusting itself to ever-expanding civilization. They are gradually being restricted to such a limited range of freedom that their future as abundant big game does not appear to be rosy.
In contrast to the bison, elk, and caribou, whose demise appeared to evoke little concern, the disappearance of deer clearly alarmed the settlers. A deer reserve was set up in Cecil County, Maryland, as early as 1661, and Massachusetts declared a closed season on deer hunting in 1694. The imposition of strict hunting laws, coupled with reintroduction efforts and forest regrowth, would eventually enable the white-tailed deer to stage a spectacular comeback. To the suburban homeowners whose ornamental shrubs are now being browsed into oblivion, the ability of the white-tailed deer to adjust to "ever-expanding civilization" is no longer in doubt.
Another group of mammals avidly sought by the settlers was the furbearers. Ermine, otter, mink, marten, fisher, wolverine, bear, wolf, lynx, raccoon, beaver, fox, and other mammals were trapped and traded with zeal wherever they were found. The Great North Woods, "that wilderness of forest lakes, of loons and geese, moose and bear" extending from the northeastern United States west to the Great Lakes and north to Hudson Bay, became the epicenter of the fur trade, yielding spectacular numbers of pelts. A sale by the famous Hudson Bay Company in November 1743 disposed of the skins of 26,750 beavers, 14,730 martens, and 1,267 wolves. Although none of these animals was driven to complete extinction by the fur trade, some were obliterated from parts of their range. The marten and fisher vanished from the Appalachian Mountains, the wolverine from northern New England and the Adirondacks.
The premier furbearer, the one whose pelt drove more people to trap in more places than any other, was the beaver. Relentlessly pursued over the course of two centuries, it was almost eliminated east of the Mississippi River by the mid-nineteenth century. Its disappearance surely had profound ecological consequences, although we are once again forced to guess at them in the absence of substantive data. The beaver is a "keystone species," an animal upon which a large number of other species depend for their survival. The ponds beavers create provide important habitats for waterfowl, herons, turtles, frogs, and fish; the trees killed by rising water levels serve as nesting and foraging sites for woodpeckers and chickadees, and as convenient perches from which hawks, flycatchers, and bluebirds watch for their prey (and for each other). None of these species is found only near beaver ponds, but all would be less common in their absenceand presumably were a century ago. Historian William Cronon suggests another, more important way in which the beaver's disappearance may have affected natural diversity in New England. When the old beaver dams finally collapsed for lack of maintenance, soils rich in the organic debris that had accumulated behind the dams were exposed. Dense grass quickly grew on the sites, providing abundant forage for domestic livestock. The exposed pond bottoms also became prime cropland for enterprising farmers. "The death of the beaver in fact paved the way for the non-Indian communities that would soon arrive."
Despite the trapping pressure, scattered populations of beavers must have persisted in the wilder corners of the Northeast, the Appalachians, and the South, for the animals have made a wonderful comeback, aided in some places by reintroduction programs. Today, watching one of the big rodents swimming along a polluted creek in the middle of Washington, D.C., it is hard to imagine that such an animal could ever be coveted, much less extirpated, for its skin.
As noted in the introduction, there is a well-established relationship between the size of an ecosystem and the number of species it sustains. This species-area relationship, which holds that a tenfold reduction in the amount of habitat results in the loss of approximately half of the species within that habitat, might lead us to expect hundreds, if not thousands, of species of plants and animals to have vanished due to deforestation in the East. But, in fact, there is no evidence of such a cataclysmic loss of wildlife. A few authors have even used the absence of a long roster of eastern extinctions as evidence that contemporary concerns about the loss of species (both in this country and elsewhere) are unwarranted. In fact, the relatively small number of forest-dwelling species that are known to have become extinct in the East does not necessarily invalidate either the species-area relationship or the angst of environmentalists. To see why this is so, we shall focus on the best-known and most intensively studied group of American animals, birds. Of the approximately 160 species of birds known to have nested in the eastern forests, only 4 are now extinct: the Carolina parakeet, passenger pigeon, ivory-billed woodpecker, and Bachman's warbler.
It comes as a surprise to most people to learn that, until the beginning of the twentieth century, a native parrot flourished in the eastern United States, ranging as far north as New York and Wisconsin and as far west as eastern Colorado. Loud and gregarious like most parakeets, it fed on the seeds of cockleburs, cypress trees, maples, elms, and other native plants, but also developed a fondness for the fruit and grain grown by settlers. Flocks of two or three hundred would descend upon orchards, where the emerald green and yellow parakeets would clamber over the branches, biting into the apples, pears, or peaches and pulling the unripe fruit off the trees. Often they were met with a volley of gunfire. Here their sociability became their undoing, for instead of fleeing, the surviving birds would circle around and screech at their fallen flockmates, permitting the shooter to kill more birds. As early as 1831, Audubon would comment upon the decline of the Carolina parakeet: "Our parakeets are very rapidly diminishing in number; and in some districts, where twenty-five years ago they were plentiful, scarcely any are now to be seen." By the end of the nineteenth century only a few birds remained, animated fugitives eagerly pursued by collectors. To Frank Chapman, preeminent ornithologist of his time, fell the dubious honor of recording the last wild flock of parakeets: thirteen birds sighted on the northeastern side of Lake Okeechobee, Florida, in April 1904. A handful of individuals survived in captivity for about a decade longer, with the last individual dying in 1918.
It is difficult to imagine that wanton shooting alone could have driven the Carolina parakeet to extinction; the species occurred over much of the Southeast, and it lived in some of our most impenetrable forests. The eventual clearing of those forests must have been an additional factor, although most ornithologists probably would rank shooting as the primary cause of its demise.
If the Carolina parakeet's disappearance is somewhat perplexing, the extinction of the passenger pigeon is, on first inspection, unbelievable. Once the most abundant bird on earth, with flocks so vast they literally darkened the midday sky, it was gone by the start of the twentieth century. Observers who witnessed the great flocks were convinced the species was all but indestructible, and the two answers put forth to explain most extinction events during this erahunting and deforestationare less than satisfying in this case. True, millions of pigeons were slaughtered, but the number taken was a small fraction of the wild population, and the birds disappeared much faster than the forests they inhabited. The key to understanding why the passenger pigeon disappeared is understanding how it lived and, in particular, its unique relationship with the beeches, oaks, and hickories that dominated upland forests in the eastern half of the continent.
All of these trees produce abundant, nutritious nuts, the mainstay of the passenger pigeon's diet. Both the trees and the pigeons shared a common survival strategy, one founded on the old adage of safety in numbers. Beeches, oaks, and hickories do not produce a steady crop of nuts each year. Instead, all of the trees of a given type in a locality will produce an enormous crop only once every few years, a phenomenon known as masting. Ecologists believe this habit arose as a defensive strategy: by flooding the area with nuts, the trees are able to overwhelm the hungry squirrels, turkeys, bears, blue jays, and other seed predators, thereby increasing the probability that at least a few seeds will survive to sprout and grow to maturity.
The passenger pigeon responded to this trick by adopting a nomadic lifestyle. During the fall and winter, flocks wandered through the eastern forests in search of masting trees, sometimes covering hundreds of miles in a day. As spring approached, they formed immense breeding colonies in areas where large crops of nuts from the previous autumn remained on the forest floor. The nests were flimsy stick platforms, and the adult birds lacked any effective means of defending them. Instead, the pigeons followed a strategy of overwhelming abundancegrouping together in colonies so vast that no predators could consume all of the eggs and nestlings. One such nesting aggregation in Wisconsin was estimated to cover more than 750 square miles and contain over 136 million birds.
Against hawks, foxes, and raccoons, the strategy was a resounding successwitness the incredible abundance of pigeonsbut against Homo sapiens it proved fatal. People besieged the nesting colonies, cutting down or burning trees filled with nests, suffocating incubating birds with sulfur, knocking young birds from their nests with poles, and luring adult birds to the ground where they could be netted. Much of this slaughter was undertaken by professional market hunters who supplied cities with pigeon meat. From a single nesting colony near Grand Rapids, Michigan, hunters shipped 588 barrelsmore than 100,000 poundsof pigeons to market.
As early as the late 1600s, natural historians along the eastern seaboard were remarking that the wild pigeons seemed much less common than in previous years, an observation they made with increasing frequency as time passed. "Some years past they have not been in such plenty as they used to be," wrote one naturalist in 1770. "This spring I saw them fly one morning, as I thought in great abundance; but everybody was amazed how few there were; and wondered at the reason." The last major nesting in New England occurred near Lunenburg, Massachusetts, in 1851. A decade later the big flocks were gone from New York and Pennsylvania. A few states passed laws to protect nesting colonies, but they were rarely enforced. More typical was the reaction of the Ohio state senate to a proposal to control, the harvest in that state: "The passenger pigeon needs no protection. Wonderfully prolific, having the vast forests of the North as its breeding grounds, traveling hundreds of miles in search of food, it is here to-day and elsewhere to-morrow, and no ordinary destruction can lessen them or be missed from the myriads that are yearly produced." In fact, the passenger pigeon was far from prolificmost pairs produced only a single offspring each yearand the destruction under way was far from ordinary. The vast majority of pigeons nested in a handful of enormous colonies scattered across the East, and it was precisely those colonies that were being targeted by hunters.
By the latter half of the nineteenth century, the northern Great Lakes states had become the passenger pigeon's last stronghold. Here the birds fell victim to two seemingly unrelated advances in technology: the expansion of the railroad and the invention of the telegraph. The railroads enabled commercial hunters to reach even the most distant colonies and ship birds back to eastern markets; the telegraph ensured that hunters quickly learned about the locations of any new colonies. The end came with remarkable speed. The total population of passenger pigeons in 1878 was estimated at 50 million birds; by the 1890s, only scattered individuals could be found. Less than one hundred days into the new century, on March 24, 1900, the last wild passenger pigeon was killed in Pike County, Ohio. The last captive individual, an aged female named Martha, died on September 1, 1914, at the Cincinnati Zoo. One would like to think that in her final months Martha invoked some measure of pity from the curious onlookers who came to see her huddled on the floor of her outdoor cage, alone and dying, immobile and inert save for the blinking of her beady eyes. Instead, the keepers had to rope off the area around the cage to keep people from throwing sand at her to make her move.
Why the pigeons disappeared so rapidly, dropping from tens of millions in 1878 to virtually none 20 years later, has long puzzled ornithologists. Recently, ornithologists David Blockstein and Harrison Tordoff have proposed a compelling explanation for that final demise. During this critical 20-year period, they suggest, hunters managed to disturb every major breeding colony for a period of time exceeding several pigeon generations. The species collapsed as entire cohorts died without replacing themselves.
Although the overwhelming majority of pigeons nested in the big colonies, a small number consistently nested in small groups or as lone pairs. Blockstein and Tordoff believe that without the safety in numbers conferred by the large colonies, these smaller groups could not produce sufficient numbers of offspring to sustain the species. Their flimsy nests and defenseless young were easy targets for predatory birds, mammals, and snakes.
The loss of the passenger pigeon must have had profound ramifications for forest ecosystems, altering the lives of predators and prey, shifting and changing the pathways of nutrients and energy in ways we will never know. One wonders what happened to the tons of mast that in years past were consumed by the pigeon flocks. Did they go into the making of more squirrels, bears, turkeys, and blue jays, animals that may have prospered from the pigeon's demise? Did oaks, hickories, or beeches increase in abundance in forest stands because more seeds were able to germinate? The questions are numerous and, for lack of evidence, timeless. Hiking through a forest today, I find it difficult to believe that the phenomenon of the passenger pigeon ever existed. Only a nation wilder and bigger than anything I am capable of imagining could have sustained the clouds of pigeons that once swept across its skies.
That wilder nation was also home to the ivory-billed woodpecker. A magnificent black bird with big white patches on its wings and neck, the ivorybill inhabited the bottomland forests of the Southeast. It was an extreme dietary specialist, feeding almost exclusively on beetle larvae that it extracted from the bark of recently deceased trees. One surmises that only the oldest forests provided sufficient food, for the woodpeckers avoided younger forests, including those that regenerated after logging. Not only did the ivorybill require old forests, it required large amounts of them. In the only scientific study of the species, completed on the eve of its extinction, biologist James Tanner calculated that its maximum density was one pair per 6.25 square miles. Even as far back as the days of Audubon, prescient observers were noting its decline. By the beginning of the twentieth century, it was a very rare bird; the last confirmed breeding records in the United States are from the early 1940s. Although it remains the Holy Grail of American birdwatchers, with persistent rumors of its presence in remote forests, most ornithologists now concede that it vanished from the United States sometime in the past 40 years. A separate population occurs in Cuba, but it too is critically endangered, if not extinct. The ivorybill belongs to a different era. Its presence today in the sterile, industrial forestlands of the South, however wonderful a thought, would be as out of place as a buckskin-clad settler with a musket in the streets of modern-day Atlanta.
The fourth bird to vanish from the eastern forests is in many ways the most mysterious. The Bachman's warbler, a 4.25-inch yellow and black songbird, nested in the bottomland hardwood forests of the southeastern United States and wintered exclusively in Cuba. First described by Audubon in 1833, it was not seen again (except for a Cuban record) for over 50 years. There followed a flurry of sightings across the Southeast, but by the 1930s the species had again become exceedingly rare. A few were seen as recently as the 1960s, but the lack of any certain reports since that time, despite growing numbers of birdwatchers, suggests that Audubon's enigmatic warbler has vanished forever. Ornithologists continue to debate the cause of its demise, with most theories focusing on the destruction of its breeding habitat, wintering habitat, or both. According to one theory, Bachman's warbler was a habitat specialist on its breeding grounds, choosing the extensive stands of wild cane (bamboo) that grew in the understory of bottomland forests in the Southeast. Much of the warbler's breeding range has been cleared to grow soybeans, rice, and other crops, and most of its wintering habitat has been converted to sugarcane. Perhaps this combination of summer and winter deforestation was sufficient to drive the species to extinction. Given that this tiny, innocuous bird was never hunted for its flesh or its plumes, it seems reasonable to presume that deforestation was the primary culprit behind its disappearance.
Thus, we have identified two birds, the ivory-billed woodpecker and Bachman's warbler, whose extinction was probably caused by the deforestation of the East, and two others, the Carolina parakeet and passenger pigeon, for which deforestation was a contributory factor. Even if we attributed the extinction of these last two species entirely to deforestation, ignoring for the moment the obvious role that overhunting played in their demise, we would still be left with a remarkably small list of birds that perished as a result of the clearing of the eastern forests. Yet by some estimates, nearly a quarter of the eastern deciduous forest was cleared between 1850 and 1909, and by the time of World War I, virtually all of it had been logged at least once. With this magnitude of forest loss, why didn't more birds (and, by extension, other types of animals) become extinct?
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DAVID S. WILCOVE is Senior Ecologist at the Environmental Defense Fund and one of the nation's foremost experts on endangered species. Among other publications, he has written for Audubon and Nature Conservancy. He lives in Arlington, Virginia.
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