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Mar.,1917 GEOGRAPHICAL VARIATION IN SPHYRAPICU$' THYIeOIDEUS ?3 Comparison of Pacific Coast with Rocky Mountain birds, hoxvever, brings forth one character, at least, serving to distinguish between the two aggregations. Relative size of bill seems to be absolutely diagnostic, the Pacific Coast bird hav- ing the bill both longer and heavier than in the Rocky Mountain race. It is no new discovery that there are differences between these two forms, for Ridgway (Birds N. and Mid. Am., v?, 1914, p. 287, footnote) gives measurements 'of series of both, and Mearns (Auk, v?, 1890, p. 252) discourses at length on differences of color and pattern that seemed to him more or less apparent. Neither author, however, deems the distinctions noted of sufficient importance to warrant divi- sion of the species nomenclaturally. The variation in bill measurement, nevertheless, is exactly comparable to what is encountered in the recognized races of the White-headed Woodpecker, .enopicus albolarvatus albolarvatus and X. a. gravirostris, the extent of differ- ence being about 'the same in each case. In this connection comparison can be made between the measurements given by Ridgway (Birds N. and Mid. Am., vx, 1914, p. 265, footnote), for the races of Xenopicus, with those of Sphyrapicus thyro?deus (loc. tit.). The differences are as worthy of recognition in one case as in the other. It is my suggestion here that the Rocky Mountain race of the Williamson Sapsucker be separately recognized on the basis of its lesser bill measurements as compared with those of Sphyrapicus thyroideus thyroideus of the Pacific Coast. As regards a name for this form, there is already one that seems to be clearly available for use. A specimen from Mexico was designated by Malherbe (Journ. fiir Orn., 1854, p. 171) as Pgcus nataliae, and an example from any part of Mex- ico (save possibly from the mountains of northern Lower California) would as- suredly be of the Rocky Mountain subspecies. Also in the measurements as given by Malherbe, length of bill ("du bee, du front 20 millimeters") places his bird unequivocally with this race. It is reasonably certain that in the Rocky Mountain region the species does not breed south of the Mogollon Divide, though it does occur as a common winter visitant in southern Arizona and over a large part of the Mexican plateau. These winter visitants, as shown by numerous specimens at hand, are migrants from the Rocky Mountain region to the northward, and not from the Pacific Coast region. So the name ?ataliae, as given by Malherbe to a Mexican specimen, can safely be used for the Rocky Mountain subspecies, which may therefore stand as Sphyra- picus thyroideus natalgae (Malherbe). Plumage variations in this species as noted in the series here assembled de- serve some comment. In a paper on Arizona mountain birds, Mearns (Auk, VlX, 1890, p. 252) carefully describes certain features of the species in which there seemed to be variation with locality. In the present connection I have made de- tailed comparison of Rocky Mountain and Pacific Coast series in regard to each of the color characters mentioned by Mearns, and failed to find even as constant or apparent difference as he did. In just one particular does there seem to be an appreciable color character. Comparing adult males from the two regions, the Rocky Mountain series as a whole certainly has the oblong abdominal patch .of a trifle darker shade of greenish yellow. In this species taken as a whole, the amount of the differences dependent on age and sex, and the extent of these as compared with similar conditions among the other forms of the genus, are of rather exceptional interest. In the early his- tory of .the bird the male and female were for years regarded as representing