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Tiny Backpacks Strapped to Songbirds Show They Fly 1,600 Miles Without Stopping

"The blackpolls just say 'the hell with it' and go for it, go for broke."
​Image: Chris Rimmer

​The blackpoll warbler is a tiny songbird that makes the rest of us look lazy as shit. Researchers say that the birds migrate 1,600 miles each year—on one, nonstop flight.

Researchers writing in the journal Biology Letters say that when the half-ounce birds head south for the winter from the northeastern United States and Nova Scotia, they fly straight out over the Atlantic to the Caribbean on a three-day, nonstop flight. After a brief Cuban vacation, they head out again to their nesting grounds in Colombia and Venezuela.

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The Canadian and American researchers put tiny, tiny half-a-gram "backpacks" containing geolocators on 19 birds. When three birds returned to New England, and two to Nova Scotia, the birds were netted again and the data was downloaded. The solar-powered geolocators used the sun to position themselves, which meant that it's not like the researchers had a down-to-the-kilometer map of where the birds were. It was clear, however, that the blackpolls were far out over the open ocean.

For years, people had suspected that the 12-gram little songbirds strayed far from land while migrating in the fall, but no one had proof. Over 50 years ago, people reported flocks of exhausted blackpoll warblers landing on the decks of ships that were far out to sea. Some showed up on Bermuda in the middle of the fall. They rarely seemed to show up in the southeastern US either.

"One final piece of evidence is that people who study birds at migration monitoring stations in places like the southern New England coasts have, for years known, that blackpolls show up, and some of them just bulk up enormously, gaining fat deposits. Some of them doubled their weight in fat," Chris Rimmer, of the Vermont Center of Ecostudies, and one of the study's authors, told me.

He said no other birds are known to be sheathed in fat like the blackpolls he's seen, and said that the birds gain fat in order to load up for a marathon.

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Though the researchers can only speculate on why the blackpolls choose to do things the hard way, Rimmer threw out a few theories for why they'd avoid working their way down Mexico and Central America.

"The advantages of this kind of strategy are that you get this perilous migration done quickly. One fell swoop," he said. "Yeah, it's risky, but you're avoiding certain other risks like predators."

Rimmer explained that most birds migrate in "hops, skips and jumps," and songbirds usually travel at night, after spending all day eating and gaining energy for the trip. There might be risk in relying on stopover points to provide food and cover and safety from predators.

"The blackpolls just say 'the hell with it' and go for it, go for broke," Rimmer said. "It's high-risk, high-reward strategy—they get down there and they get it over with and they get to their wintering grounds early."

While knowing that a tiny bird can make a 1,600 mile flight is without a doubt cool, Rimmer explained that the knowledge may also prove pretty important from a conservation standpoint. Rimmer explained that the abundant blackpoll warbler is found from Alaska all the way over to Vermont. It's not endangered, but its numbers are declining at a rate of about 5 to 6 percent per year and no one is sure why. Knowing its whole life cycle will help conservationists better track why the blackpoll warblers are dying.

"It could be where these birds are congregating before they strike out on this flight—on the coast of Massachusetts, Connecticut, or Long Island—maybe there's been so much development that they can't find the resources they used to that allowed them to bulk up for the journey," Rimmer speculated as an example. "Or maybe when they reach Hispanola—Haiti and the Dominican Republic have a tremendous loss and development of their natural forests—what if the exhausted warblers reach there after a three-day, 1,600 mile flight and can't find a good patch of habitat? We can now begin to think about where we need to pay attention."

So, yeah, there's practical considerations here. But also, on a base level, it's also worth noting that the blackpoll warbler apparently evolved to just say "to hell with it" and fly 1,600 miles without stopping. It took us until geolocating technology evolved down to tiny backpack size just to confirm it.