Its known as "Flight(as in fleeing) Molt"
In 1842, Elias Loomis performed an experiment that left much to be desired in the control of experimental variables. It received wide attention at the time. His goal was to gain insight into the wind speed needed to defeather a chicken. An account written a few years later states: "In order to determine the velocity needed to strip feathers, the six-pounder (cannon) was loaded with five ounces of powder, and for a ball a chicken was killed. The gun was pointed upwards and fired. The feathers rose twenty or thirty feet and were scattered by the wind. On examination, they were found to be pulled out clean, the skin seldom adhering to them. The body was torn into small fragments, only a part of which could be found. The velocity was 341 miles per hour." Loomis speculated that if a live bird was fired at 100 miles per hour, the results would be more successful, but, to my knowledge he never attempted it. He did place dead chickens under a vacuum jar to see if the feathers would explode. They did not. A widely accepted alternative theory in the 19th century was that opposing electric charges during the tornado's passage stripped feathers from chickens and tore the clothes from people. It was supposed that the highly charged tornado induced an opposite charge in objects as it approached and things would be sent flying. While static electricity is undoubtedly present in a debris filled funnel, this makes no scientific sense whatever. There is simply no mechanism that would produce powerful opposing charges on the bird and on the feather at the same time.
The most likely explanation (Vonnegut, 1965) for the defeathering of a chicken is the protective response called "flight molt." Chickens are not stripped clean, but in actuality they lose a large percentage of their feathers under stress in this flight molt process. In a predator-chicken chase situation, flight molt would give the predator a mouth full of feathers instead of fresh fowl. In a tornado, the panicked chicken's feathers simply become loose and are blown off. Stories of chickens found dead, sitting at attention and stripped clean of feathers may be on par with reports of the blowing of a cow's horn or a two-gallon jug being blown into a quart bottle without cracking
