Vol. 54, pp. 211-216 December 8, 1941 PROCEEDINGS BIOLOGICAL^^;^j(§PTMt JJ^gf/j^^JNGTON W IIZ 3 1941 NOTES ON TOXOSmMyJ^lf^VWetl^TRE OF MEXICO, WITH DESCRIPTION OF A NEW RACE. BY ROBERT T. MOORE, California Institute of Technologij. A misconception of the relationship of the races of Toxostoma curvirostre in Mexico has hindered progress in our understanding of this group, a misconception due to lack of adequate material. With one hundred and twenty-eight recently taken specimens in the Moore Collection, covering every race, except that of extreme northeastern Mexico, from which last area fresh material has recently been received on loan, it is now possible to assess the characters of the races more correctly. The chief misconception has been the behef that the bird of southern Sinaloa, Toxostoma curvirostre occidentale (type locahty Mazatlan, Sinaloa) has white tips to the rectrices. Our very large series from Sinaloa proves that occidentale has grayish-brown tips, if any, there being only one speci-men with a white tip out of thirty-five in our collection. Therefore, the chief character, on which Ridgway (Bull. 50, U. S. Nat'l Mus., Pt. IV, 202 and Key pp. 186-187) relied to distinguish between occidentale and maculatum of southern Sonora is non-existent. We have a single aberrant specimen, taken on April 5th within twenty miles of Alamos, type locality of maculatum, which has large immaculately white tips, just as we have one taken close to the type locality of occidentale, but all the rest of our large series of both races, even in fresh fall plumage, have either no tips or decidedly buffy ones. The true white-tipped birds seem to consist chiefly of two groups, — (1) those of the Central Plateau at high elevation, ranging from Guanajuato and Aguascalientes north, which in fresh plumage have immaculately white tips, and (2) those of northeastern and eastern Mexi-co; all of them east of the main Sierra Madres of Mexico, this section of the backbone of the continent being the dividing line between the white-tipped and buffy-tipped groups. The undescriljed form of the Central Plateau, lying between oberholseri to the north and true curvirostre to the south, is a larger bird than either, 47— Pboc. Biol. Soc. Wash., Vol. 54, 1941. (211)
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