The tiny migratory bird, called the arctic tern, makes the longest migration of any animal in the world-flying about two times farther than previously thought, a new study has revealed. By attaching miniature new transmitters, the researchers revealed that the 4-ounce (113-gram) bird follows zigzagging routes between Greenland and Antarctica each year. In the process, the arctic tern covers about 44,000 frequent flier miles (71,000 kilometers), beating its archrival, the sooty shearwater, by roughly 4,000 miles (6,440 kilometers).
“There have been all kinds of theories, but now, for the first time, we’ve been able to show what the birds are doing out there,” National Geographic News quoted the lead author of the study, Carsten Egevang of the Greenland Institute of Natural Resources, as saying.
As the birds are known to live for 30 years or more, the researchers have estimated that, over its lifetime, an arctic tern migrates about 1.5 million miles (2.4 million kilometers)-equal to three trips to the moon and back.
The researchers used a tiny tracker developed by the British Antarctic Survey, which weighs just a twentieth of an ounce (1.4 grams)-light enough for an Arctic tern to carry on a band around its leg.
And surprisingly, the researchers found that the birds often stop for a month in the open North Atlantic Ocean, probably to “fuel up” on fish and small crustaceans before setting off to cross the tropics.
Arctic terns also follow a zig-zagging route on their spring trips back to Greenland. Rather than flying straight up the middle of the Atlantic, the birds hopscotch from Antarctica to Africa to South America to the Arctic. “It’s a detour of several thousand kilometres. But when you analyze it, it makes perfect sense,” said Egevang. The birds appear to be following huge spiralling wind patterns in the atmosphere, avoiding flying into the wind, he said.
Regardless of the route, there isn’t any viable reason as to why arctic terns have such a long migration in the first place.
“My gut feeling is that it’s because of the rich [polar] feeding grounds that they travel so far,” said Egevang.
The study’s findings have been published in the journal Proceedings of the National Academy of Sciences.