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Defenders Magazine
Into the Blue
Can the cerulean warbler overcome the long odds against it?
On a warm June morning, with gathering clouds threatening a storm, my wife and I emerged from the woods onto a small rocky overlook. It had been a steep climb. Below us, the crumpled landscape of West Virginia spilled to the horizon: jumbled, heavily forested mountains encircling small valley fields. The trees were full of bird song—the fluting of wood thrushes, the dry trills of worm-eating warblers.
But one song caught Amy’s sharper ear, a high-pitched, buzzy melody that one early naturalist likened to a bird singing, “Just a little sneeze!” A moment later we saw a flash of sky-blue and white, as the singer darted across the opening and paused briefly on an oak branch. It was a male cerulean warbler, newly returned from South America, reasserting his territorial rights to this Appalachian ridgetop—and marking a red-letter morning for us.
Time was when this “heavenly-blue wood warbler” (in the words of early-20th-century ornithologist Arthur Cleveland Bent) would have been a common sight. Though easy to overlook in the treetops, the cerulean warbler was among the most abundant and widespread of all migrant songbirds flooding north each spring from the tropics.
Today, however, it a rare bird, and rapidly getting rarer. Its population has plummeted an estimated 70 percent since the 1960s—the worst decline of any neotropical migrant—propelled by habitat loss in North and South America. This worrisome trend shows no sign of stopping—especially not here in West Virginia, a crucial cerulean stronghold where entire mountaintop forests are being blasted to rubble in a horrific form of coal mining.
Conservationists, alarmed at the cerulean warbler’s precipitous decline, have tried—thus far unsuccessfully—to force the federal government to protect the bird under the Endangered Species Act. In the absence of government action, various groups and individuals are taking whatever steps they can to reverse the long, sad slide of this lovely bird.
By its very nature, a cerulean warbler’s life is a seemingly endless challenge. Twice each year this slender songbird, barely four and a half inches long and named for the faded denim color of the males, makes an astonishing migration between the forests of eastern North America and the misty foothills of the northern Andes. Even though an adult cerulean warbler weighs just 10 grams—barely more than three pennies—it makes a round-trip flight of as long as 6,000 miles every year, including two 600-mile nonstop flights across the Gulf of Mexico, dodging storms, exhaustion and predators along the way.
How did the situation become so bleak for such a widespread bird? Unfortunately, every step of the cerulean warbler’s life history puts it at risk, starting with the breeding season. Found from southern New England west to Minnesota and south through Arkansas, the warbler has always done best in stands of mature hardwood forest with great structural complexity, including emergent canopy trees and small, sapling-choked gaps.
Defending Cerulean Warblers
With numbers of the once-ubiquitous cerulean warblers falling for several decades, Defenders of Wildlife and a host of other conservation groups petitioned the federal government to list the bird as a threatened species in 2000. After six years of waiting, the U.S. Fish and Wildlife Service finally decided last year that it would not list the species. The service reasoned that since the species was not in imminent danger of extinction, a listing would be premature.
"While there may be some species that face more immediate threats to their continued existence than the cerulean warbler, potentially none would have benefited more than the cerulean from the protections afforded a listed species," says Andrew Hawley, staff attorney for Defenders.
Defenders of Wildlife remains committed to saving the cerulean warbler and its threatened habitat, Hawley says, and will continue to explore all options—including the possibility of legal action—to reach that goal.
Unfortunately, those old-growth woodlands began to fall as soon as European settlers arrived. Ceruleans were especially common in the ancient bottomland forests of the Mississippi and Ohio valleys, forests that were all but annihilated in the 19th- and early 20th centuries; the species is now rare in much of this part of its former domain. Today, the heart of the cerulean’s range is the hilly Appalachian plateau country, stretching from Tennessee and Kentucky up through West Virginia and Pennsylvania.
They still need large expanses of mature forest, though—an increasingly scarce resource. Cerulean warblers are sensitive to any fragmentation of their forest home, and in some regions will usually shun tracts smaller than several thousand acres. Farming, roads, sprawl development and logging have all had a significant impact on cerulean warbler habitat, but the looming threat today is an appallingly destructive type of mining.
Known as mountaintop removal, it entails blasting the upper several hundred feet of an Appalachian ridge into rubble, which is pushed into the adjacent valley to expose a seam of coal. What had been a vertical landscape of rich hardwood forests and rushing streams is turned into a ragged, sterile plateau reseeded in grass.
“The estimate is that between 1992 and 2012, 1.4 million acres of cerulean warbler habitat will have been destroyed, half of it by mountaintop mining,” says Caroline Kennedy, senior director of field conservation programs for Defenders of Wildlife. Such a loss could eliminate up to a fifth of the remaining warbler population.
The trouble doesn’t stop once the birds leave the breeding grounds, either. Like most songbirds, ceruleans migrate at night, and many die when they collide with tall communications towers, whose lights dazzle and confuse the birds. Wind turbines, which are rapidly increasing in number through the East, may also pose a threat, though the degree to which they are a hazard to nocturnal birds remains unclear. (It’s ironic that wind energy, being promoted as an alternative to coal, can itself cause habitat problems of a different sort—the turbines, situated in large clearings strung out for miles through ridgetop forests, and connected by roads and utility corridors, can fragment critical cerulean warbler habitat.)
As trans-Gulf migrants, ceruleans require high-quality habitat along the Gulf Coast, so they can fatten up before and after making the exhausting, 24- to 40-hour overwater crossing. Sadly, more and more coastal land is growing condos, vacation homes and casinos, instead of the fertile hackberry and live oak thickets these and many other migrant birds need.
If they make the journey to South America safely, the birds next find themselves in the crosshairs of the global cocaine economy. They winter in a narrow zone within the Andes, on the middle and lower slopes of the mountains—exactly the area being stripped of its forest cover to grow coca, from which cocaine is made. Sun-coffee plantations and cattle pastures add to the habitat loss.
Data from the annual Breeding Bird Survey, conducted across North America every year since 1966, suggest that cerulean warbler populations have declined nationally by as much as 70 percent, and by as much as 80 percent in the birds’ historic core range.
“One of the commonsense tenets of conservation is that to prevent a species from declining, you should protect the places where the largest numbers occur,” says Jeffrey Wells, songbird biologist and author of Birder’s Conservation Handbook: 100 North American Birds at Risk. “Yet in the case of the cerulean warbler, the place of its highest abundance is being destroyed.”
Nationally, cerulean numbers continue to fall at about 3 percent or 4 percent a year, according to federal surveys. Given that grim assessment, in October 2000 Defenders of Wildlife, along with the Southern Environmental Law Center, Audubon and 25 other conservation organizations, filed a petition with the U.S. Fish and Wildlife Service to list the cerulean warbler as “threatened” under the federal Endangered Species Act.
If the service listed the warbler, it would be required to take action on the bird’s behalf—drafting a recovery plan, for instance, and coordinating with other federal agencies involved with forestry, land management and mining to safeguard the remaining populations. Instead—despite repeated threats of lawsuits—the agency dragged its feet for almost six years before announcing, last December, that it was refusing to list the warbler.
Ironically, the agency agreed that there was no reason to expect the decline to stop without further action. At current rates, government officials said, the cerulean warbler population a century from now could be a mere 15,000 birds—down from nearly half a million today, and a tiny fraction of the warbler’s original numbers. But, the agency reasoned, because the species wasn’t likely to be completely extinct then, there was no reason to grant it federal protection now.
Despite setbacks at the federal level, bird conservationists throughout the Western Hemisphere have mobilized on the cerulean warbler’s behalf. They have made the species one of their highest priorities for research and management, and the Bird Conservation Alliance (a network of almost 200 conservation organizations including Defenders, coordinated by the American Bird Conservancy) has chosen the cerulean warbler as the focus for its 2007 international appeal.
The alliance is raising money to purchase critical wintering habitat in Ecuador and Colombia, including an expansion of the existing Cerulean Warbler Bird Reserve in the Rio Chucurí basin of Colombia, the only sanctuary in Latin America dedicated to a neotropical migrant. (The reserve also shelters many resident bird species, including the endangered gorgeted wood-quail.)
While cerulean warblers prefer untouched forest in South America, they will use tropical woodlands that shelter shade coffee plantations. So one easy way individual conservationists can help this species (and many others) is to buy shade-grown coffee.
Efforts to protect the warbler’s North American habitat continue. A U.S. district court in March blocked coal companies from continuing to bury headwater streams beneath mountain mine rubble. Similar rulings have been overturned in the past, however, and the case may be appealed. The Bush administration has actually loosened the regulations on this kind of mining, which at current rates will destroy more than 2,200 square miles of forest by 2012, the Environmental Protection Agency estimates.
There is some good news from the breeding grounds: Surveys suggest that cerulean warblers may be expanding in range and numbers in the Northeast, pushing into areas where they may not have occurred in the past. This tiny increase hardly cancels out the huge and continuing losses in traditional regions like the Mississippi Valley and Cumberland Plateau, but every little bit helps for this small bird that is staring down large odds.
For now, the experts remain deeply concerned. Says Wells: “For the cerulean warbler, habitat destruction at such a magnitude as we’re seeing from mountaintop-removal mining makes the species’ long-term prospects especially worrisome.”
