Things We Learned Today

And you thought your family station wagon logged a lot of miles. Arctic terns fly 44,000 miles every year—that’s three trips to the moon and back over one tern’s lifetime. The longest annual migration in the world takes the terns from pole to pole and includes stops in the middle of the North Atlantic Ocean and the Weddell Sea on the shores of Antarctica.

Scientists from the British Antarctic Survey mapped the migratory route with a tiny tracking instrument known as a geolocatoraffixed to the terns’ legs and published the findings earlier this month. Results of the study proved surprising.

Among the discoveries, the birds travel an average of 300 miles a day, which, of course, is nothing to those of us with parents who insisted on making it from New England to Disney World in one shot. But terns, lacking a 20-gallon tank, must rely on a mere two-foot wingspan and the food they find along the way.

Flying southward toward Antarctica, the scientists found that flocks split up with one half traveling down the African coast and the other half traveling down the South American coast. And, on the return journey, rather than making a beeline home, they traced out a gigantic "S" pattern northward through the Atlantic Ocean—a detour of several thousand miles indicating that Arctic terns use prevailing global winds to conserve energy on their long flight north.

While the American family trip is characterized by few stops except the one for milk that, exasperatingly, happens nearest home, the shape of the Arctic tern’s route is determined by both winds as well as the biological richness of the waters they pass, which explains their month-long layover in the fruitful waters in the middle of the North Atlantic. That will all change, of course, if terns ever discover the MiniMart.