1) Rising currents 2) Warm undergarments 3) Wintertime underwear 
a heated column of air that moves up from the earth's surface
heated air that rises off the earth - birds will ride these columns of air
columns of warm air that rise when the ground is heated by the sun. Raptors take advantage of these upward air movements to gain altitude during migration. The birds circle upward within the column of rising air and then glide down to the base of another thermal