° 8 " I RiDGWAY, Geographical Variation in Sialiamexicava. I C C 



Sialia cceriileocollis Vig. Zool. Voy. Blossom, 1839, 18, pi. 3 (Cali- 

 fornia?). 1 



Sialia mexicana (nee Swains.) Gamb. Proc. Ac. Nat. Sci. Philad. Ill, 

 1846, 113 (California) ; Jour. Ac. Nat. Sci. Phil. I, 1847, 37 (do.). — 

 Scl. P. Z. S. 1S57, 126 (California); 1859, 235 (Vancouver I.). — 

 Baird, B. N. Am. 1S5S, 223; Cat. N. Am. B. 1859, No. 159; 

 Review, 1S64, 63. — Coop. Orn. Cal. I, 1S70, 28. — Coues, Key, 1872, 

 76; 2d ed., 1S84, 25S; Check List, 1873, N °- 17; 2ded. 18S2, No. 2S; 

 B. N. W. 1874, 14; B. Col. Val. 1S7S, 80.— B. B. & R. Hist. N. 

 Am. B. I., 1874, 65, pi. 5, fig. 2.— Lawr. Mem. Bost. Soc. N. H. 

 II, 1874, 267 (Mazatlan; plains of Colima 2 ).— Ridgw. Norn. N. 

 Am. B. 1881, No. 23; Man. 1887, 581. — Anthony, Zoe, IV, No. 3, 

 1893, 247 (San Pedro Martir Mts., Lower Cal.; common during 

 migrations). 



Geographical Distribution. — Western United States in general (in 

 wooded districts), north to British Columbia, east to Colorado, western 

 Texas, and New Mexico, south to San Pedro Martir Mts., Lower Cal- 

 ifornia, western and northern Mexico (Mazatlan, Colima, Sonora, 

 Chihuahua and Cohahuila). Apparently breeding to nearly the southern 

 limit of its range. 3 



Subsp. Char. — Smaller than true 5. ?nexicana, with the blue color of 

 upper parts much lighter (ultramarine or light smalt blue instead of deep 



1 "Sial. capite, gula, collo, corporeque superiori casruleis ; dorso interscapular! 

 brunnescenti ; pectore abdominisque lateribus runs, hoc imo albescenti. 



"Longitude corporis, 61-4; rostri, 5-8; alae, a carpo ad apicum remigis secundae, 

 4 1-2; caudse, 3; tarsi, 7-8. 



"This species may be distinguished from the Sylvia sialis, Lath., which forms the 

 type of Mr. Swainson's genus Sialia, by the blue color of the throat in front, and the 

 brown color of the back. The bill is also slighter than in the latter bird. A young 

 specimen, or perhaps a female of the species, is in the collection, which has the 

 colours much less vivid than in the adult bird ; the rufous color of the lower body 

 seems also to extend further up the throat. It, however, evinces its distinction from 

 the young of the allied species by the slighter bill, and by a white mark extending 

 over the outer web of the interior quill-feathers, at their base." (VIGORS, 1. c.) 



No locality is mentioned, but the specimens on which the above descriptions were 

 based were either from California or the west coast of Mexico. 



2 I have not seen Col. Grayson's Mazatlan specimens, but an adult male and female 

 collected by Xantus on the plains of Colima, in October, 1863, now in the National 

 Museum Collection, are of this form. 



3 An adult female from Saltillo, Cohahuila, obtained by Lieut. Couch in May, 1853 

 is in worn breeding plumage. Even in the San Pedro Martir Mountains, Lower 

 California, where it is said to be "very common during migrations from sea level to 

 the top of the range," a few remain, according to Mr. Anthony (1. c.) "to nest with the 

 local race." 



