North American birds on the decline
Nearly a third of native bird species - even common ones - are seeing striking losses, says a survey.
Nearly two centuries ago, vast herds of buffalo were almost wiped off the face of America's great plains by settlers. Today it's the prairie chicken that's getting plucked.
Once plentiful like the buffalo, the prairie chicken was dubbed the "fool's hen" because it was so easy to shoot. Even so, the delectable but hardy species survived. As recently as the 1980s, healthy numbers could be found "booming" their songs across the plains.
But a new survey shows that the greater prairie chicken species is in trouble. Since 1966, its population has fallen 78 percent. Fewer than 700,000 individual birds remain. It's a fate shared by many species - from the cerulean warbler to the chimney swift to the northern bobwhite.
In a striking trend that spans North America's key ecosystem regions - grassland, shrubland, forest, wetland, and urban - almost a third of 654 bird species native to North America are in "statistically significant decline," according to a first-ever "State of the Birds" report unveiled last month by the Audubon Society.
"We've painted a picture people didn't know before - that there's a big fraction of our bird populations that are facing serious problems," says Greg Butcher, a wildlife biologist and author of the report, which draws on decades' worth of data from major bird population surveys.
Grassland species are in the most trouble, with 19 of 27 species analyzed - 70 percent - in significant decline since 1966. But what's affecting the prairie chicken and other grassland species is not a single cause - such as too much hunting - but instead a "perfect storm" of habitat loss, predators, and changing farming and ranching practices, researchers say.
Ironically, the resurgence of some predator birds, such as hawks, have made it harder for prairie chickens to find a peaceful home on the range. More intense cattle grazing, proliferating power lines, roads, fencing, housing, and shopping malls - even huge new electrical wind generators - have added to the pressure.
The lesser prairie chicken, in rapid decline like the greater prairie chicken, instinctively resists nesting anywhere near trees or man-made structures - especially tall towers or buildings, where birds of prey can perch and spot them below, according to recent studies by Kansas State University biologists.
"One of the biggest threats on the horizon is wind farms," says Steve Sherrod, executive director of the George Miksch Sutton Avian Research Center in Bartlesville, Okla. "These wind farms are billed as green, but they're a huge threat to the prairie nesting species."
Other grassland birds are similarly affected. The bobolink, for instance, nests in hayfields and northern grasslands of the United States. But more frequent haying, overgrazing, and other man-made changes have combined to cut its population in half to about 11 million, the report says.
Similar declines show up in other ecosystems. The northern bobwhite, a common bird with a call familiar to millions, prefers shrublands - sagebrush and chaparral - which span 20 percent of the Lower 48 states. Yet conversion of shrublands to grazing and ill-timed burning of farm fields have cut its numbers by more than two-thirds to 9 million.
Woodland species are struggling, too. In the Appalachian forests, the cerulean warbler is threatened by mountaintop mining, its population falling nearly 80 percent since 1966 to about 560,000 birds today. Meanwhile, the pine siskin, a woodland finch common at backyard bird feeders, fell by more than half to about 22 million birds, the report says.
Such drops are relatively recent. Far larger declines in bird populations occurred before bird surveys were common. The postwar shift from family farms to industrial farming brought massive bird mortality on the grasslands. Flocks seen today are just a shadow of the size of bird populations in North America's recent past, researchers say.
"What we're looking at in this era is habitat loss due to intense economic use of the land," Mr. Butcher says. "Obviously, urban expansion is tremendously important. But it's the farming, logging, [and] mining that's really affecting large numbers of birds."
Not all bird populations are dwindling. Of 45 urban species tracked, for example, 44 are considered of "low or no concern" in terms of the health of overall population numbers.
There are several success stories, too. By the 1950s and 1960s, bluebirds had disappeared from large parts of their range. But bluebirds rebounded strongly as Boy Scouts and bluebird societies put up houses for the species in the 1970s and 1980s, providing a substitute for the nesting cavities of old-growth trees that had been logged.
The whooping crane, which numbered just 14 to 16 birds in 1941, has rebounded to about 300 today. Many predatory birds - including the city-dwelling peregrine falcon, bald eagle, and brown pelican - have undergone a steady recovery since the pesticide DDT was banned in 1974. Double-crested cormorants, nearly extinct in the 1960s, are today considered a pest by fishermen.
Still, many experts find the new report sobering. "This is a major step forward, a first realization that we as a society have to pay attention to these birds," says Russell Greenberg, director of the Smithsonian Migratory Bird Center. "This analysis should show us that we can't just ignore all birds except the endangered species and the game birds."
Ignored species are something Dr. Greenberg knows a bit about. For years he was nearly alone in studying the plight of the rusty blackbird.
The "rusty" isn't a typically beautiful songbird - its call sounds like "a creaking, rusty gate," Greenberg says. In some states it is even classified as "vermin" that can be exterminated freely. Only its rusty scaling and yellow eyes set it apart from other blackbirds.
But something mysterious has slashed 98 percent of its population in just under four decades - putting it at the top of Audubon's list of fast-declining species. Is it logging in Canada's boreal forest where the rusty breeds in the spring? Parasites? Whatever it is, it threatens to extinguish the rusty soon if something isn't done, Greenberg says.
What heartens Butcher is that birds have shown they can bounce back if humans meet them halfway. Getting farmers and ranchers to time brush burning to accommodate the prairie chicken would be a good first step, he adds.
"These North American birds can withstand a lot of insult without going extinct," Butcher says. "So if we change our ways we have a chance to save them and allow the populations to rebound."