Mar., 1917 GEOGRAPHICAL VARIATION IN SPHYRAPICUS THYROIDEUS 63 



Comparison of Pacific Coast with Rocky Mountain birds, however, 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., vi, 1914, p. 287, footnote) gives measurements of series 

 of both, and Mearns (Auk, vn, 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, 

 Xenopicus 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., vi, 

 1914, p. 265, footnote), for the races of Xenopicus, with those of Sphyrapicus 

 thyroideus (loc. cit). 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. 

 fur Orn., 1854, p. 171) as Picus 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 nataliae, as given by Malherbe to a Mexican specimen, can safely be 

 used for the Rocky Mountain subspecies, which may therefore stand as Spliyra- 

 picus thyroideus nataliae (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, vu, 

 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 



