The Song Sparrow (Melospiza melodia) is one of the most morphologically variable birds of North America. As many as 52 subspecies have been named, 39 of which were recognized by the American Ornithologists’ Union (AOU 1957) and Paynter (1970) from Canada, the United States, Baja California, and central Mexico. In the latest taxonomic revision of the Song Sparrow, Patten and Pruett (2009) recognized 25 subspecies. The subspecies vary from small and pale in the desert Southwest (fallax) to large and dark in the Aleutian Islands (maxima), with a wide range of intermediates and other variations. Although the Song Sparrow has little or no prealternate molt, the appearance of the basic plumage, especially in subspecies of more open and drier habitats, is affected by wear. The upperparts generally become paler (grayer or browner) and less distinctly streaked from fall to spring, while the underparts become whiter (less buff or brownish) and more distinctly streaked in spring. The subspecies are migratory to various degrees, with some being resident, while others are short-distance or medium-distance migrants (AOU 1957, Arcese et al. 2002).