During the fall of 2009, three tiny Alaskan songbirds took an amazing three-month journey that began on a windswept dome northeast of Fairbanks and ended amid the arid grasslands of the southern Sudan in Africa — a 9,000-mile trip that traversed mountain ranges and deserts, including the Arabian Peninsula.
Then, once their winter sojourn in the Old World ended, the 25-gram birds — chirpy Northern wheatears that each weighed about as much as a couple of moose nuggets — flew back across the Asian landmass.
Destination? Another summer of insect-scarfing bliss amid the New World tundra at Eagle Summit.
This 18,000-mile round-trip migration between sub-Arctic Alaska and sub-Saharan Africa might make these striking passerines the world's champion avian sightseers, according to a new tracking study published this week in the journal Biology Letters.
The findings, made possible by ultra-lightweight tracking devices, also offered stunning new insight into migratory abilities of songbirds like the wheatear, whose wintering grounds were previously unknown but thought to be somewhere in the Eastern Hemisphere.
"Our results provide the first incontrovertible evidence that a migratory songbird regularly travels between Arctic regions of the Western Hemisphere and Africa," wrote the study's eight German and Canadian authors in the conclusion of "Cross-hemisphere migration of a 25 g songbird."
"Scaled for body size, this is the one of the longest round-trip migratory journeys of any bird in the world and raises questions about how a bird of this size is able to successfully undertake such physically demanding journeys twice each year, particularly for inexperienced juveniles migrating on their own."
The same team of scientists also tracked a covey of wheatears from a separate population on Baffin Island in the high Canadian Arctic and found a similar epic trip that led to a different winter destination in western Africa. The single bird that returned with retrievable data had flown more than 2,100 miles over the Atlantic Ocean en route, a crossing that took four days of nonstop travel.
Incredible journeys for a bird the weight of a candy bar
"They are incredible migratory journeys, particularly for a bird this size," said biologist Ryan Norris, a co-author of the study and a professor of integrative biology at the University of Guelph in Ontario, in this story. "Think of something smaller than a robin but a little larger than a finch raising young in the Arctic tundra and then a few months later foraging for food in Africa for the winter.
"This is the only known terrestrial bird that physically links the two radically different ecosystems of the Old World and the Arctic regions of the New World," Norris added.
Details about the songbird's migration remained largely unknown because devices that could track movements were too bulky, explained a story about the research. But "new smaller devices now allow scientists to track flights over several months and over long distances."
The gizmos — called "geo-locators" — weighed only about 1.2 grams or about 1/25th of an ounce. They attach to the birds with a harness that loop the legs and don't substantially interfere with the animal's ability to fly or forage for food. (An equivalent device carried by a 180-pound scientist might weigh as much as a laptop computer, a bottle of water and a tuna sandwich, about eight pounds.)
As the birds winged across the world, the geo-locators recorded natural light levels twice each day for 90 days, data that was later used to calculate the birds' location on the surface of the globe. The scientists also collected feathers of the birds as they arrived in the Arctic and analyzed them for trace chemicals of the food at winter destinations.
"Chemical signatures in the feathers come from certain geographic locations, allowing scientists to learn where the birds spent the winter without directly tracking them," this story explained.
Behind the project was a mystery: Northern wheatears were thought to winter in the Old World because no one had ever found them in North America. No one knew where. To find out, the researchers attached the geo-locators to 30 birds in Eagle Summit in Alaska in 2009, and to another 16 wheatears on Baffin Island in Nunavut in 2010.
Five of the Alaska birds returned the following year, the authors reported. One couldn't be caught, and another had lost its geolocator. But the scientists successfully recaptured three of the birds and downloaded data from the tiny devices.
Mystery birds: Where did the Northern wheatears go?
What they found stunned the scientists.
"The AK birds spent their winter in eastern Africa somewhere in Sudan or Uganda/Kenya," the authors wrote. "During the autumn, birds traveled through northern Russia and Kazakhstan before crossing the Arabian Desert, a one-way trip that averaged (about 9,000 miles and took 91 (plus or minus 11) days. … The same route was followed during the spring but the duration was approximately one month shorter."
When on the move, the birds averaged up to 100 miles per day, sometimes flying across some of the most desolate landscapes on Earth.
Of the 16 birds tagged on Baffin Island in 2010, only two returned in 2011 — and only one retained its tracking device. That particular bird took a European jaunt before wintering in western Africa.
"The CN bird appeared to cross about (2,100 miles) from Baffin Island to the western British Isles in no more than four days … possibly via Greenland … and continued south through Europe for another (2,500 miles) to spend the winter … on the coast of Mauritania," the authors wrote.
Why would a relatively small bird undertake such long trips to find summer food and mating grounds? Why not target winter or summer habitats much closer together? Why not, for instance, spend the snow season in North America, like scores of other Arctic species?
The scientists say it's likely the birds originally did migrate a much shorter distance — between Africa and the tundra of Ice Age Europe. As the ice retreated over thousands of years, the ice-edge tundra retreated with it, and the birds continued to fly northwest and northeast to until they found its current location.
Because the birds were capable of such a feat, no evolutionary pressures drove them to find other seasonal homes.
"The migratory journeys from both sides of the Western Hemisphere Arctic to sub-Saharan Africa could be a consequence of the Pleistocene expansion of the breeding range," the scientists wrote in the paper. "The fact that Western Hemisphere wheatears have not colonized America during the winter suggests that selection has not acted against what appears to be a well-developed innate migratory programme."
News of the discovery spread to dozens of web outlets this week, lighting up media in Europe and North America. It was heralded as much as a triumph of ingenious miniaturization in tracking technology as a biological coup.