The "swan maiden" is a tale classified as ATU 400, "The Swan Maiden" or "The Man on a Quest for His Lost Wife", in which a man makes a pact with, or marries, a supernatural female being who later departs. The wife shapeshifts from human to bird form with the use of a feathered cloak. The discussion is sometimes limited to cases in which the wife is specifically a swan, a goose, or at least some other kind of bird, as in Enzyklopädie des Märchens.