Whooper
Swan

They have been recorded migrating at elevations up to 27,000 feet — nearly the height of Mount Everest—to catch jet streams and bypass weather systems.

During long migrations, whooper swans can sleep while flying by resting one side of their brain at a time while the other half stays alert.

Weighing up to 20 to 31 pounds with a wingspan of nearly 8 feet, they are among the heaviest flying birds in the world.