The World Without Us

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.