This is Birdnode. The sight of hundreds of vultures slowly circling overhead might seem

pretty ominous, but most of the time it just means the vultures are on their way somewhere

else. In the daytime hot air rises as the sun heats the ground. The rising column of

air is called a thermal and it's the perfect way for a turkey vulture to hitch a ride.

Like an elevator to the skies, the thermal gently wafts the vultures upward. They move

in a slowly ascending spiral around the thermal, rarely flapping and instead coasting on the

breeze. When many vultures ride the same thermal, it's called a kettle. During raptor migration,

turtles can swell with many different raptor species, like this Swanson's Hawk. Hawk see

the swirling vultures and join in, taking the opportunity to save their energy. The

air current lifts the birds hundreds or thousands of feet of the air before pedering out. Finally,

the raptors lead the thermal and glide downward for miles. Often far enough to take them

to another thermal. Thermals make raptor migration a breeze and a spectacle for observers

on the ground. For bird note, I'm Michael Stein. Support for bird note is provided by Jim

and beer to Faulkner and generous listeners around the world.