The blackpoll warbler is a small songbird that weighs 12 grams, the equivalent of two nickels and a dime. But there’s nothing diminutive about this bird’s amazing migration abilities. A new study shows that they are capable of flying more than 1,500 miles nonstop, from the forests of New England and eastern Canada to the Caribbean, en route to its wintering ground in South America.
Proportional to its weight, this is the longest nonstop migration for any bird in the world, says Ryan Norris, an ecologist at Ontario’s University of Guelph.
The birds make this incredible journey by flying nonstop, day and night, over the course of two to three days. They prepare for it by putting on an extra five to six grams of fat to provide them with energy, and some have even been recorded doubling their bulk before setting off, according to the study, published in the journal Biology Letters.
“Even if I locked myself in a McDonald’s for two weeks I could not accomplish this feat,” says Bridget Stutchbury, a researcher at York University in Ontario who wasn’t involved in the study.
Until recently, it wasn’t possible to accurately monitor these tiny birds during their long journey, since tracking equipment was too heavy. But the scientists showed that it is possible to trail these warblers using a small, newly developed device that weighs only 0.5 grams (one-fifth the weight of a penny).
The researchers outfitted 37 birds, half from Vermont and half from eastern Canada, with these geolocators in the autumn. In the spring, they recovered five of them, says study co-author Chris Rimmer, a scientist at the Vermont Center for Ecostudies.
Why the small birds make such an audacious journey over the Atlantic, when they could just fly along the coast or further inland, isn’t known for sure, Rimmer says. But the scientists have a few guesses. “It may be that there’s an advantage to getting the migration done quickly, in ‘one fell swoop,’ so to speak,” Rimmer says. Such a journey is, after all, hazardous—the birds are more prone to predation and death from the elements outside their forest home. Out over the ocean, they are likely less prone to predators, he says. But they will, of course, die if they can’t make it; they aren’t capable of resting in the water like some waterfowl, Rimmer adds.
Other small birds also make long journeys. A species known as the northern wheatear is known to fly 2,000 miles nonstop from Canada to the United Kingdom, for example, Norris says. But they are significantly larger.
“Gram for gram, this astounding journey is far more impressive than the days-long flights of larger shorebirds,” Stutchbury says. “This bird inspires our respect and amazement, but with this should come a sense of responsibility. Blackpoll warblers are declining by about 6 percent per year, and their Achilles’ heel could very well be the key stopover sites where they refuel before and after this marathon flight.” The latter include Long Island and Puerto Rico, where habitat loss may be playing a role in their shrinking numbers.