Arctic Researchers Race to Uncover Effects of Global Warming on Songbirds
Ornithologists are in a race against time to document shifts at the top of the world that could foreshadow what's to come in lower latitudes.
Marcel Visser, an evolutionary ecologist from the Netherlands Institute of Ecology, has studied various avian species, including the pied flycatcher, a migrant that overwinters in Africa and breeds in Northern Europe every spring, and the great tit, a widespread resident of Europe, Asia, and the Middle East. In a 2006 study in Nature, Visser and colleagues reported a 90 percent decline among nine Dutch populations of the pied flycatcher in areas where food availability peaked too early due to warmer spring temperatures. By contrast, in areas where no mismatch occurred, the team found little to no population decline. In more recent studies, Visser and his colleagues have documented shifts in seasonal timing in various bird species, including great and blue tits. While some appear to be keeping up with the changes, others are not.
Migratory songbirds are particularly vulnerable, says Visser, because day length, rather than temperature, is their cue for when to leave their winter residences. "The problem for long-distance migrants is they have to make a decision about their timing in a very different place than where it really matters, which is in the breeding area," he says. The fact that the Arctic is warming so fast is a "ticking time bomb" for migratory birds, "because these birds are not taking temperature into account."
Cagan Sekercioglu, a bird conservation ecologist at the University of Utah, has studied birds the world over and recently compiled a comprehensive database of the ecology and ecological functions of most of the world's 10,000 bird species. In a 2008 paper in Conservation Biology, Sekercioglu and his colleagues modeled and analyzed potential extinction rates of more than 8,400 land birds, representing 87 percent of all bird species, under 60 different scenarios, including variables such as warming projections, habitat loss, and shifts in elevation ranges. In the team's worst-case scenario, some 2,500 bird species--or almost a third of the world's land-bird species--could be committed to extinction by the year 2100 if no conservation actions are taken.
"Since 2008 a lot of things have headed in the wrong direction," says Sekercioglu, including rising greenhouse gas emissions and waning political will toward an international agreement to limit those greenhouse gases. Yet there are positive signs, he adds, such as a recent Nature study showing that the most extreme projections are looking less likely. And in June President Obama committed to leading international efforts to address global climate change when he rolled out his ambitious global warming action plan.
"Climate change threatens all our victories in bird conservation and introduces new challenges related to shifting ranges and the ecosystems that birds and people depend on," says Gary Langham, vice president and chief scientist of the National Audubon Society. Because Alaska is the headwaters of the migratory bird flyways, the state is at the forefront of Audubon's concerns about climate impacts, says Langham. "A thorough understanding of how birds will respond to the uncertain climate future allows Audubon to make wise conservation investments to save the future of our birds."
On another warm day at a field site about 20 miles farther south, the researchers are checking on several nests they found the week before and hunting for new ones. Some of the students head off with sweep nets to collect bugs and to check pitfall traps, while others use metal poles to probe the brush for sparrows or longspurs. Boelman and Wingfield inspect their equipment, including an acoustic device with microphones and a recording unit that captures birdsong in order to document the presence of particular species at various times throughout the summer.
At this site, webs of snow still cling to the mountains in narrow rivulets. Green moss blankets the hillsides until the hills become barren peaks, jutting into the clouds. We spot swallows, a sandpiper, and a long-tailed jaeger with boomerang-like wings and a showy plume of ribbon extend- ing from its tail. Fireweed--dainty wildflowers with fuchsia blossoms--and the tiny pink bells of bog rosemary dot the landscape. One of the only visible reminders of humans is hard to miss: the trans-Alaskan pipeline, which zigzags like a giant metal snake across the hilly plains, carrying crude oil southward to Valdez.
After scouring an area for a half-hour and crawling on all fours, the researchers find an impossibly camouflaged white-crowned sparrow nest in a thicket of shrubs. Closer inspection reveals five lightly speckled eggs, about a half-inch long, nestled inside. By the end of June the team has found 20 sparrow nests and 27 longspur nests.
What the researchers are learning at the top of the world will provide key information to plug into global ecosystem models, which will then generate better forecasts. And it will give conservationists and wildlife managers a clearer idea of what's to come--perhaps allowing time to preserve species in the Lower 48, where shifts aren't occurring as rapidly. Ultimately, though, climate change is a radical experiment with nature. In a sense, all the researchers can do is continue to wait. If the birds start missing lunch, they'll be right there, watching and, perhaps, even hoping.
This story originally ran in the September-October 2013 issue as "Out of Sync."