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> This shows how frigate birds stay aloft so long by riding thermals: - http://www.agnosticweb.com/index.php?mode=posting&id=22993&back=entry - Frigatebirds spend weeks or even months at a time cruising above open ocean, spearing fish from the surface. Their voyages take them far from any place to rest, and the birds can&apos;t swim, which has made their feats of endurance a biological puzzle.   Ornithologist Henri Weimerskirch of the French National Centre for Scientific Research (CNRS) and colleagues fixed GPS trackers, accelerometers, and heart rate monitors to frigatebirds to track their travels and energy expenditure. In a study published this summer (July 1) in Science, the researchers reported that the birds spent about as little energy soaring hundreds of miles every day as they would sitting at rest.  - Their trick is to ride thermal currents upward for thousands of feet and then glide down while the enormous birds prowl for prey, the authors found. An instinctive sense for atmospheric patterns appears to guide the birds&apos; flight pattern, as they reliably skirt equatorial doldrums, where updrafts are few and far between. - The birds displayed another feat of aerial acumen: flying into the center of cumulus clouds where turbulent currents push them as high as 2.5 miles. &#147;It&apos;s the only bird that is known to intentionally enter into a cloud,&#148; Weimerskirch told NPR&apos;s All Things Considered, adding: &#147;there is no other bird flying so high relative to the sea surface.&#148; - Comment: Using my same judgmental requirements, once again this looks like a learned instinctual behaviour, because flying into a cloud does not affect survival and can develop an epigenetic learned pattern.