Head-scratching method of the Swainson's warbler

Ficken and Ficken (Auk, 85: 136, 1968) suggest that the "Head-scratching method may prove a valuable addition to the set of complex characters that can be used in defining genera," and that field observers should continue to fill gaps in our knowledge of this behavior. In the course of a series of observations of Swainson's Warblers (Limnothlypis swainsonii) in the Dismal Swamp, Virginia, I saw head-scratching in three individuals, four times in one, three in another, and once in the third. All three birds used the direct method, bringing the foot forward and under the wing.