The World Without Us - Alan Weisman (2007)

Part III

Chapter 14. Wings Without Us

1. Food


T THE WESTERN end of the Korean DMZ, on a mud-pancake island in the Han River estuary, nests one of the rarest large birds of all: the black-faced spoonbill. Only 1,000 remain on Earth. North Korean ornithologists have clandestinely warned colleagues across the river that their hungry comrade citizens swim out to poach spoonbill eggs. The South Korean hunting ban is no help, either, to geese that land north of the DMZ. Nor do cranes there banquet on rice kernels spilled by mechanized harvesters. The reaping in North Korea is all by hand, and people take even the smallest grains. Nothing is left for birds.

In a world without humans, what will be left for birds? What will be left of birds? Of the more than 10,000 species that have coexisted with us, ranging from hummingbirds that weigh less than a penny to 600-pound wingless moas, about 130 have disappeared. That is barely more than 1 percent, almost an encouraging figure if some of these losses hadn’t been so sensational. Moas stood 10 feet tall and weighed twice as much as an African ostrich. They were extinguished within two centuries by Polynesians who sometime around AD 1300 colonized the last major planetary landmass that humans discovered, New Zealand. By the time Europeans appeared some 350 years later, piles of big bird bones and Maori legends were all that remained.

Other massacred, flightless birds include the dodo of the Indian Ocean’s Mauritius Island, famously clubbed and cooked to death within a hundred years by Portuguese sailors and Dutch settlers it never learned to fear. Because the penguin-like great auk’s range stretched across the upper Northern Hemisphere, it took longer, but hunters from Scandinavia to Canada managed to exterminate them anyhow. The moa-nalo—flightless, oversized ducks that ate leaves—went extinct long ago in Hawaii; we know little about them, other than who killed them.

The most stunning avicide of all, just a century ago, is still hard to fathom in its enormity. Like hearing astronomers explain the entire universe, its lesson gets lost because its subject, when it was alive, literally exceeded our horizons. The postmortem of the American passenger pigeon is so fertile with portents that just a brief glance warns—screams, in fact— that anything we consider limitless probably isn’t.

Long before we had poultry factories to mass-produce chicken breasts by the billion, nature did much the same for us in the form of the North American passenger pigeon. By anyone’s estimate, it was the most abundant bird on Earth. Its flocks, 300 miles long and numbering in the billions, spanned horizons fore and aft, actually darkening the sky. Hours could go by, and it was as though they hadn’t passed at all, because they kept coming. Larger, far more striking than the ignoble pigeons that soil our sidewalks and statuary, these were dusky blue, rose breasted, and apparently delicious.

They ate unimaginable quantities of acorns, beechnuts, and berries. One of the ways we slew them was by cutting their food supply, as we sheared forests from the eastern plains of the United States to plant our own food. The other was with shotguns, spraying lead pellets that could down dozens with a single blast. After 1850, with most of the heartland forest gone to farms, hunting passenger pigeons was even easier, as millions of them roosted together in the remaining trees. Boxcars stuffed with them arrived daily in New York and Boston. When it finally became apparent that their unthinkable numbers were actually dropping, a kind of madness drove hunters to slaughter them even faster while they were still there to kill. By 1900, it was over. A miserable few remained caged in a Cincinnati zoo, and by the time zookeepers realized what they had, nothing could be done. The last one died before their eyes in 1914.

In succeeding years, the parable of the passenger pigeon was retold often, but its moral could only be heeded in part. A conservation movement founded by hunters themselves, Ducks Unlimited, has bought millions of acres of marshland to insure that no game species they value will be without places to land and breed. However, in a century in which humans proved more inventive than during the rest of Homo sapiens history combined, protecting life on the wing became more complicated than simply making game-bird hunting sustainable.

Passenger pigeon. Ectopistes migratorius.


2. Power

The Lapland longspur isn’t commonly known to North Americans, because its behavior isn’t quite what we expect from migratory birds. Its summer and breeding grounds are in the high Arctic, so just as more familiar songbirds head toward the equator and beyond, Lapland longspurs arrive to spend the winter in the great plains of Canada and the United States.

They’re pretty little black-faced, finch-sized birds with white half masks and russet patches on their wings and nape, but we mostly see them at a distance: hundreds of indistinct, small birds swirling in the winter prairie wind, picking over fields. On the morning of January 23, 1998, however, they were easy to see in Syracuse, Kansas, because nearly 10,000 were lying frozen on the ground. During a storm the previous evening, a flock crashed into a cluster of radio-transmission towers. In the fog and blowing snow, the only things visible were red, blinking lights, and the longspurs apparently headed for them.

Neither the circumstances nor the numbers of their deaths were particularly unusual, although the toll for a single evening was possibly high. Reports of dead birds heaped around the bases of TV antennae started getting ornithologists’ attention in the 1950s. By the 1980s, estimates of 2,500 deaths per tower, per year, were appearing.

In 2000, the U.S. Fish and Wildlife Service reported that 77,000 towers were higher than 199 feet, which meant that they were required to have warning lights for aircraft. If calculations were correct, that meant that nearly 200 million birds collided fatally with towers each year in the United States alone. In fact, those figures had already been usurped, because cell phone towers were being erected so fast. By 2005, there were 175,000 of those. Their addition would raise the annual toll to half a billion dead birds—except that this number was still based on scant data and on guesses, because scavengers get to most feathered victims before they’re found.

From ornithology labs east and west of the Mississippi, graduate students were sent on grisly night missions to transmitter towers to recover the carcasses of red-eyed vireos, Tennessee warblers, Connecticut warblers, orange-crowned warblers, black-and-white warblers, ovenbirds, wood thrushes, yellow-billed cuckoos . . . the lists became an increasingly thorough compendium of North American birds, including rare species like the red-cockaded woodpecker. Especially prominent were birds that migrate, and especially those that travel at night.

One is the bobolink, a black-breasted, buff-backed plains songbird that winters in Argentina. By studying its eyes and brains, bird physiologist Robert Beason has detected evolutionary traits that unfortunately turned lethal in the age of electronic communications. Bobolinks and other migrants carry built-in compasses—particles of magnetite in their heads, with which they orient to the Earth’s magnetic field. The mechanism to switch them on involves their optics. The short end of the spectrum—purples, blues, and greens—apparently triggers their navigational cues. If only longer red waves are present, they grow disoriented.

Beason’s observations also suggest that migrating birds evolved to fly toward light in foul weather. Until electricity, this meant the moon, which would put them out of harmful weather’s way. Thus, a pulsating tower bathed in a red glow whenever fog or blizzard blots out everything else is as seductive and deadly to them as wailing Sirens to Greek sailors. With their homing magnets befuddled by a transmitter’s electromagnetic fields, they end up circling its towers, whose guy wires become the blades of a giant bird blender.

In a world without humans, the red lights will blink off as broadcasts cease; a billion daily cellular conversations will disconnect, and several billion more birds will be alive a year later. But as long as we’re still here, transmission towers are only the beginning of the unintended carnage human civilization perpetrates on feathered creatures we don’t even eat.

A different kind of tower—frameworks of steel lattice averaging 150 feet tall, spaced every 1,000 feet or so—marches the length and breadth and diagonally across every continent save Antarctica. Suspended between these structures are aluminum-clad high-tension cables bearing millions of sizzling volts from power plants to our energy grids. Some are three inches thick; to save weight and cost, all are uninsulated.

There’s enough wire in North America’s grid alone to reach the moon and back, and nearly back again. With the clearing of forests, birds learned to perch on telephone and power lines. As long as they don’t complete a circuit with another wire or with the ground, they don’t electrocute themselves. Unfortunately, the wings of hawks, eagles, herons, flamingos, and cranes can span two wires at once, or brush an uninsulated transformer. The result is no mere shock. A raptor’s beak or feet can melt right off, or its feathers can ignite. Several captive-bred California condors have died exactly this way on being released, as have thousands of bald and golden eagles. Studies in Chihuahua, Mexico, show that new steel power poles act like giant ground wires, so that even smaller birds end up on the piles of dead hawks and turkey vultures below.

Other research suggests that more birds die by simply colliding with power lines than from being zapped by them. But even without webs of live wires, the most serious traps for migratory birds await in tropical America and Africa. So much land there has been cleared for agriculture, much of it for export, that each year there are fewer roosting trees to ease the journey, and fewer safe wetlands where waterfowl can pause. As with climatic change, the impact is hard to quantify, but in North America and Europe, the numbers of some songbird species have fallen by two-thirds since 1975.

Without humans, some semblance of those wayside forests will return within a few decades. Two other major perpetrators of songbird loss— acid rain, and insecticide use on corn, cotton, and fruit trees—will end immediately when we’re gone. The resurgence of bald eagles in North America after DDT was banned bodes hopeful for creatures that cope with residual traces of our better life through chemistry. However, while DDT is toxic at a few parts per million, dioxins become dangerous at just 90 parts per trillion—and dioxins may remain until the end of life itself.

In separate studies, two U.S federal agencies estimate that 60 to 80 million birds also annually end up in radiator grilles or as smears on windshields of vehicles racing down highways that, just a century ago, were slow wagon trails. High-speed traffic would end when we do, of course. However, the worst of all man-made menaces to avian life is totally immobile.

Well before our architecture tumbles, its windows will mostly be gone, and one reason will be repeated pounding from inadvertent avian kamikazes. While Muhlenberg College ornithologist Daniel Klem was earning his doctorate, he enlisted suburban New York and southern Illinois residents to record the numbers and kinds of birds crashing into that post—World War II home builder’s icon, the plate glass picture window.

“Windows are not recognized as obstacles by birds,” Klem tersely notes. Even when he stood them in the middle of fields, free of surrounding walls, birds failed to notice them until the final, violent second of their lives.

Big birds, little birds, old or young, male or female, day or night—it didn’t matter, Klem discovered over two decades. Nor did birds discriminate between clear glass and reflective panes. That was bad news, given the late-20th-century spread of mirrored high-rises beyond city centers, out to exurbs that migrating birds recall as open fields and forests. Even nature park visitor centers, he says, are often “literally covered with glass, and these buildings regularly kill birds that the public comes to see.”

Klem’s 1990 estimate was 100 million annual bird necks broken from flying into glass. He now believes that 10 times that many—1 billion in the United States alone—is probably too conservative. There are about 20 billion total birds in North America. With another 120 million taken each year by hunting—that same pastime that snuffed mammoths and passenger pigeons—these numbers begin to add up. And there is still one more scourge that man has wreaked on birdlife, one that will outlive us—unless it runs out of birds to devour.

3. The Pampered Predator

Wisconsin wildlife biologists Stanley Temple and John Coleman never needed to leave their home state to draw global conclusions from their field research during the early 1990s. Their subject was an open secret—a topic hushed because few will admit that about one-third of all households, nearly everywhere, harbor one or more serial killers. The villain is the purring mascot that lolled regally in Egyptian temples and does the same on our furniture, accepting our affection only when it pleases, exuding inscrutable calm whether awake or asleep (as it spends more than half its life), beguiling us to see to its care and feeding.

Once outside, however, Felis silvestris catus drops its subspecies surname and starts stalking as it reverts to being F. silvestris—wild cat— genetically identical to small native wildcats still found, though seldom seen, in Europe, Africa, and parts of Asia. Although cunningly adapted over a few thousand years to human comforts—cats that never venture outdoors generally live far longer—domestic cats, Temple and Coleman report, never lost their hunting instincts.

Possibly, they sharpened them. When European colonists first brought them, American birds had never before seen this sort of silent, tree-scaling, pouncing predator. America has bobcats and Canadian lynx, but this fecund invasive feline species was a quarter-size version—a frightening, perfect fit for the enormous population of songbirds. Like Clovis Blitzkriegers, cats killed not only for sustenance, but also seemingly for the sheer pleasure of it. “Even when fed regularly by people,” Temple and Coleman wrote, “a cat continues hunting.”

In the past half-century, as the world’s human population doubled, the number of cats did so much faster. In U.S. Census Bureau pet figures, Temple and Coleman found that from merely 1970 to 1990, America’s cat count rose from 30 to 60 million. The actual total, however, must also include feral cats that form urban colonies and rule barnyards and woodlands in far greater densities than comparable-sized predators like weasels, raccoons, skunks, and foxes, which have no access to protective human shelter.

Various studies credit alley cats with up to 28 kills per year. Farm cats, Temple and Coleman observed, get many more than that. Comparing their findings with all the available data, they estimated that in rural Wisconsin, around 2 million free-ranging cats kill at minimum 7.8 million, but probably upwards of 219 million, birds per year.

That’s in rural Wisconsin alone.

Nationwide, the number likely approaches the billions. Whatever the actual sum may be, cats will do very well in a world without the people who took them to all the continents and islands they didn’t already inhabit, where they now outnumber and out-compete other predators their own size. Long after we’re gone, songbirds must deal with the progeny of these opportunists that trained us to feed and harbor them, disdaining our hapless appeals to come when we call, bestowing just enough attention so we feed them again.

IN FOUR DECADES of birding, ornithologist Steve Hilty, author of two of the world’s thickest field guides (to the birds of Colombia and Venezuela), has seen some strange human-caused changes. He’s watching one of them from the shore of a glacial lake just outside the town of Calafate in southern Argentina, near the Chilean border: kelp gulls from Argentina’s Atlantic coast, which have now spread across the country and grown 10 times more abundant simply from scavenging landfills. “I’ve watched them follow human trash across Patagonia like house sparrows going after spilled grain. Now there are far fewer geese on lakes, because gulls prey on them.”

In a world without people’s garbage, guns, and glass, Hilty predicts a reshuffling of populations back toward their former balance. Some things may take longer, as temperature shifts have done funny things to their ranges. Some brown thrashers in the southeastern United States today don’t bother to migrate, and red-wing blackbirds have even passed up Central America to winter over in southern Canada, where they now encounter a classic southern U.S. species, the mockingbird.

As a professional birding guide, Hilty has watched the decline of songbirds tilt into a plunge that has even nonbirders noticing the deepening silence. Among the missing in his native Missouri is our only blue-backed, white-throated warbler. Cerulean warblers used to depart the Ozarks each fall for mid-elevation Andean forests in Venezuela, Colombia, and Ecuador. With more of those being cut each year for coffee—or coca—hundreds of thousands of arriving birds must funnel into an ever-shrinking wintering ground, where there isn’t enough to feed them all.

One thing still heartens him: “In South America, very few birds have actually gone extinct.” That is huge, because South America has more bird species than anywhere. When the Americas were joined 3 million years ago, just below the juncture at Panama was mountainous Colombia, poised to be a giant species trap, with every niche from coastal jungle to alpine moor. Colombia’s number-one rank—more than 1,700 bird species—is sometimes challenged by ornithologists in Ecuador and Peru, which means that even more vital habitat still remains. Yet too often, just barely so: Ecuador’s white-winged brush finch now lives in only one Andean valley. Northeast Venezuela’s gray-headed warbler is confined to a single mountaintop. Brazil’s cherry-throated tanager is found on just a single ranch north of Rio.

In a world without people, the birds that survived would soon reseed South American trees that were displaced by rows of that Ethiopian immigrant Coffea arabica. With no one there to weed, new seedlings would battle coffee bushes for nutrients. In a few decades, shade from their canopies would slow the interloper’s growth, and their roots would strangle it until it choked.

Coca plants—native to the highlands of Peru and Bolivia, but needing chemical help anywhere else—won’t last two seasons in Colombia without men to tend them. But dead coca fields, like cattle pastures, will leave a checkerboard of empty bald spots where forest clandestinely came down. One of Hilty’s biggest concerns is for small Amazonian birds so adapted to dense cover that they can’t tolerate bright light. Many fail because they won’t cross open areas.

A scientist named Edwin Wills discovered that, just after the Panama Canal was completed. As Lake Gatun filled, some mountains ended up as islands. The biggest, 3,000-acre Barro Colorado, became a research laboratory for the Smithsonian’s Tropical Studies Institute. Wills began to study foraging antbirds and ground cuckoos—until suddenly they were gone.

“Three thousand acres weren’t enough to sustain a population of species that won’t cross open water,” says Steve Hilty. “In forest islands separated by pastures, it’s the same.”

The birds that manage to survive on islands, as Charles Darwin momentously observed among finches in the Galápagos, can adapt so tightly to local conditions that they become species unto themselves, found nowhere else. Those conditions explode, however, once humans arrive with their pigs, goats, dogs, cats, and rats.

In Hawaii, all the roast feral pig devoured in luaus can’t keep up with the mayhem their rooting wreaks on forests and bogs. To protect exotic sugarcane from being eaten by exotic rats, in 1883 Hawaiian growers imported the exotic mongoose. Today, rats are still around: the favorite food of both the rat and the mongoose is the eggs of the few native geese and nesting albatrosses left on Hawaii’s main islands. In Guam, just after World War II, a U.S. transport plane landed bearing stowaway Australian brown tree snakes in its wheel-wells. Within three decades, along with several native lizards, more than half the island’s bird species were extinct, and the rest designated uncommon or rare.

When we humans become extinct ourselves, part of our legacy will live on in the predators we introduced. For most, the only constraints on their rampant proliferation have been the eradication programs with which we’ve tried to undo our damage. When we go, those efforts go with us, and rodents and mongooses will inherit most of the South Pacific’s lovely isles.

Although albatrosses spend most of their lives on their majestic wings, they still must land in order to breed. Whether they will still have enough safe places to do so is uncertain, whether we’re gone or not.