The shortest journey was 36,900 miles and the longest was 50,700 miles. The study confirmed what researchers suspected for decades, the Arctic Tern has the longest annual migration of any animal in the world. Over its life time the Arctic Tern files the equivalent of three trips from the Earth to the Moon and back.

The birds do not just fly south. They spend about a month in the middle of the Atlantic Ocean. They spend this time feeding to “fuel up” before they continue to fly into the waters of the South Atlantic which have less food sources for them.

After this pause, the birds continued their long journey south down the coast of northwest Africa. However, around the Cape Verde Islands — islands off the west coast of Africa, close to Senegal — the birds’ behavior surprised the research team again. About half of the birds continued down the coast of Africa, while the other half crossed the Atlantic Ocean to follow a parallel route south down the east coast of South America. All of the birds went to the Antarctic waters, none of them stayed at any location along the their route.

After spending the summer at the South Pole on their return trip to the North Pole they did not follow the most direct route back to their breeding grounds in Iceland. Instead they flew a gigantic “S” pattern through the Atlantic Ocean. This route added several thousand miles to the birds flight back to their breeding grounds. This indirect  route allowed the birds to take advantage of the global wind system and to reduce the amount of energy they need to use on their return journey.

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