[A golden eagle soars on a thermal. It occasionally flaps its wings several times, then continues gliding. It moves its tail to steer. A common raven is sometimes visible, also soaring on a thermal.] 

End of transcript

This Golden Eagle may appear to be floating, but it is actually riding on rising columns of warm air known as thermals. Thermals are generated when the sun warms the earth’s surface, indirectly heating the air closest to the ground, causing it to rise. Soaring birds can use this rising air to gain elevation and remain aloft for extended periods without flapping their wings.

This video accompanies Chapter 5, Avian Flight, Handbook of Bird Biology, 3rd Edition, from the Cornell Lab of Ornithology and Wiley Publishing.

Recorded by Eric Liner