The Arctic Tern's 44,000-Mile Round Trip

Every year, a small seabird called the Arctic Tern flies from the top of the world to the bottom and back again. That round trip is about 44,000 miles, longer than flying around the whole Earth twice! Over its life of 30 years, one tern can fly far enough to reach the Moon and come back three times. Why would a bird fly so far? The answer is a clever trip called migration.

1. What migration is and why birds do it. 2. How birds find their way across huge distances without a map. 3. Examples of real migrating birds and the amazing distances they travel.

Migration means moving from one place to another when the seasons change. Birds do it mainly to find food and warmer weather. In the far north, summer is full of bugs and daylight, perfect for raising babies. But when winter comes, the bugs vanish and it gets freezing cold. So the birds fly south to places where food is easy to find. When summer returns up north, they fly back. The Arctic Tern chases summer at both ends of the planet, so it almost never sees winter!

Birds do not carry maps, yet they travel the exact same routes every year. Scientists have found they use several tools at once. Many birds use the Sun and the stars like a compass. Others can sense the Earth's magnetic field, an invisible force that points the way like a hidden arrow. Some follow landmarks such as coastlines and mountains. Young birds often follow older, experienced ones the first time, learning the route.

The Bar-tailed Godwit holds a record for the longest nonstop flight ever recorded: one bird flew about 8,435 miles from Alaska to Tasmania in 11 days without landing or eating even once. The tiny Ruby-throated Hummingbird, which weighs less than a nickel, crosses 500 miles of open water over the Gulf of Mexico in a single flight. Big or small, migrating birds are true endurance athletes.