Nuthatches of the genus Sitta constitute one of the passerine groups in which prealternate (prenuptial) molt is generally believed not to occur. Dwight (1900: 298) discussed this genus with the family Paridae and stated: "All the members of this family have only the annual moult. They are peculiar in assuming a juvenal plumage closely resembling the pale nuptial plumage which results from extreme fading of the winter dress." Witherby (in Witherby et al. 1938: 244) remarked that in S. europaea the summer plumage is attained by abrasion rather than by molt. Following Dwight's analysis, Bent (1948) recorded that the prenuptial molt did not occur in S. carolinensis or S. canadensis. Although Norris (1958: 246) found several females of S. pygmaea that were replacing feathers in the nuchal region in March and April, he regarded this as a regrowth of feathers lost in social interactions rather than as prealternate molt; the replacement of contour feathers "over nearly every part of the body" in early April by one female of that species was considered to be "an aberrant instance of prenuptial molt." Norris (op. cit.) stated categorically that "There is no prenuptial molt in Sitta pusilla." For most species in the genus, however, I have been unable to find any statement, even a negative one, concerning the occurrence of this molt. On the other hand, there is a partial prealternate molt in the seasonally dimorphic Tichodroma muraria, usually considered a member of the family Sittidae but in a different subfamily.
