My two favorite glider stories: (condensed)

From Nat. Geo., way back.

Guy soared the entire lenght of the Appalchians (or some such distance), read the wind by looking at the color change of the leaves on the trees below as the wind blew across them.

Anothe guy was soaring in California and started watching sea gulls soaring. So, he followed one off shore. He began to wonder and sure enough, after awhile, the bird turned around and started flapping its wings! He made it back okay but made a mental note not to follow sea gulls.