In Search of Refuge
The cerulean warbler encounters habitat pressures throughout the year, both north and south of the equator.
A neotropical excursion to South America may seem like a trip to paradise, but for the cerulean warbler, that exotic travel destination is not so accommodating. Not only does the tiny songbird face habitat loss in its breeding range in North America—from mountaintop removal mining and the timber industry, for example (“Free Fall,” Field Notes)—it’s also under pressure in its southern wintering grounds. “They’re kind of getting a double whammy,” says David Buehler, a professor of wildlife science at the University of Tennessee. “They’ve got to deal with it on both ends of their life history.”
The cerulean prefers Andean forests in Colombia, Venezuela, Peru, Ecuador, and to a lesser extent Bolivia, where it can be found at elevations of between 1,500 to 5,500 feet—the same range favored by human populations and the agricultural industries—particularly coffee. At least 70 percent of what was thought to have been original cerulean habitat has been deforested.
“The birds and the people are in a situation where they’re trying to share space,” says Paul Hamel, a wildlife biologist working with El Grupo Ceruleo, a subcommittee of the Cerulean Warbler Technical Group (made up of agencies, scientists, Audubon and other conservation groups, universities, nongovernmental organizations, and timber industry representatives) and concerned specifically with the activities of the bird in its wintering range.
Scientists recognize that conservation is necessary to stem the bird’s decline (about 3 percent each year), but what makes it difficult is limited historical research on the bird. “That’s the classic catch-22,” says Jason Jones, a biology professor at Vassar College who, up until three years ago, was the only North American ornithologist to have studied the bird in South America.
|This gorgeted wood-quail is one of several critically endangered species that share space with the cerulean warbler in the Cerulean Warbler Bird Reserve.
Courtesy of Fundación ProAves
In recent years, however, the cerulean’s plight in its wintering range has garnered more interest, and researchers are making a concerted effort to learn more about the bird’s biology—such as its foraging behavior and distribution—in order to develop appropriate conservation programs.
For example, researchers working with El Grupo Ceruleo have developed a model to predict where the cerulean might be concentrated, based on historical and current records on where the bird has been spotted. They’re now testing it to see if its predictions correspond with where the bird is actually found. Once the model is refined, researchers might be able to use it to guide where—and how—conservation efforts should proceed.
Work done by Amanda Rodewald, a wildlife ecologist with Ohio State University, and her doctoral student Marja Bakermans, who split their time between Venezuela and the United States, also suggests that some ceruleans return to the same spot each year—both on the breeding and the wintering grounds—which has implications for the conservation of specific sites.
Some of those sites could include shade coffee plantations. Indeed, up until a few years ago, researchers thought that the cerulean needed mature Andean forests to survive, but surveys now suggest that the bird can also live amid the trees provided by some shade coffee plantations, as opposed to the more common sun coffee plantations, which Rodewald says offer “no forest habitat at all.”
A suffering coffee market, however, is forcing many planters in the northern Andes to convert their shade plantations to sun or to pastures for livestock—and convincing them to maintain their shade plantations is not always easy. “The problem of conservation is a problem of economy in [the neotropics],” says Gabriel Colorado, a forest engineer who works with El Grupo Ceruleo.
A view of the Cerulean Warbler Bird Reserve, which occupies 500 acres of subtropical forest in the Rio Chucurí basin of Santander, Colombia.
Courtesy of Fundación ProAves
Conservationists and researchers hope that by educating local planters about the importance of shade to the cerulean and by working with coffee cooperatives to develop shade-grown coffee that can be sold at a higher price, growers will resist the urge to switch to sun. “We are in the middle between the coffee growers and the international market,” says Maria Isabel Moreno, a conservation biologist with ProAves, a nonprofit organization based in Colombia dedicated to the study and conservation of birds. Cerulean Conservation Coffee is one cerulean-friendly coffee already on the market. Introduced by ProAves and the American Bird Conservancy, the coffee is shade-grown in a Colombian region where the cerulean is known to occur.
Taking strides to protect the cerulean has the added benefit of protecting other native birds—another angle conservationists are pursuing. In 2005, ProAves, along with the ABC, created The Cerulean Warbler Bird Reserve in a subtropical forest in Colombia; while the reserve is the first in Latin America to protect a songbird that breeds exclusively in North America, it also encompasses several critically endangered bird species such as the gorgeted wood-quail, the Colombian mountain grackle, and the chestnut-bellied hummingbird.
Setting aside land for reserves, however, is not that simple, given the dependence of farmers on the Andean terrain. They “need something to eat,” says Colorado. “We cannot throw away people from their land.”
Even if the obstacles to understanding cerulean biology and conservation in South America are overcome, there’s still the question of what’s happening while the bird is in flight—that is, during its intercontinental migration. For example, it’s unclear how many ceruleans stop along their arduous flight, and for how long.
With so many uncertainties, it might seem hard to keep an optimistic outlook for such a small bird. “If you’re a ‘glass-half-empty’ person you’d be going ‘why bother?’” says Jones. But given the recent growth in cerulean interest from scientists, conservationists, and even coffee planters, Jones claims there’s ample room for hope: “I think our best days are ahead of us.”
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Feature story link to "Free Fall."