140 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



KEY TO SPECIES AND SUBSPECIES OP SIAIJA. 



a. Plumage without streaks. (Adults.) 



b. Pileum and liindneck bright hlue, like rump, etc. (Adult males.) 

 c. Under parts partly chestnut or cinnamomeous. 



d. Throat cinnamomeous, like chest and sides. {Sialia sialis.) 



e. Throat, chest, and sides deep vinaceous-rufous or cinnamon-chestnut; 

 wing averaging 100.3, tail 03.6. (Eastern United States; Bermu- 

 das. ) Sialia sialis sialis, adult male ( p. 142) 



ee. Throat, chest, and sides light rufous-cinnamon; wings and tail longer. 

 /. Blue of upper parts lighter and greener (averaging cerulean or light co- 

 l)alt); wing averaging 103.9, tail 66.9. (Mexican plateau, north to 



southern Arizona) Sialia sialis fulva, adult male (p. 146) 



//. Blue of upper parts deeper and more violaceous (averaging ultramarine 

 or french blue, as in S. s. sialis); wing averaging 105.5, tail 68.1. 

 (Highlands of Guatemala and Honduras.) 



Sialia sialis guatemalae, adult male (p. 147) 

 fid. Throat l)lue. {Sialia mcxicana.) 



e. Larger (wing averaging 109 or more, tail averaging more than 67). 

 /. Cinnamon-rufous of under parts more restricted, the center of breast 

 (sometimes also median line of chest) blue; smaller (wing averaging 

 less than 111, tail averaging less than 70). 

 g. Back entirely blue, or with hardly more than a trace of chestmit on 

 each side of interscapular region; chestnut or cinnamon-rufous of 

 chest usually interrupted in middle l>y extension of lilue of throat 

 to that of lireast. 

 /;. Bill smaller or more slender; blue of upper parts averaging more 

 violaceous (smalt). (Northeastern portion of Mexican plateau.) 

 Sialia mexicana mexicana, adult male (p. 148) 

 hh. Bill larger, stouter; blue of upper parts averaging lighter or less 

 violaceous (ultramarine). (Mountains of northern Lower Cali- 

 fornia, extreme southern California, and eastern slope of Sierra 



Nevada.) Sialia mexicana anabelae, adult male (p. 150) 



gg. Back entirely, or mostly, chestnut; chestnut or cinnamon-rufous of 

 chest not interrupted. (Rocky Mountains of United States, south 

 of Montana, and Sierra Madre of northwestern Mexico.) 



Sialia mexicana bairdi, adult male (p. 152) 

 ff. Cinnamon-rufous of under parts nu)re extensive, occupying whole of 

 chest, breast, sides, and flanks; larger (wing averaging more than 116; 

 tail averaging more than 71). (Southern portion of Mexican plateau.) 

 Sialia mexicana australis, adult male (p. 154) 

 ee. Smaller (wing averaging 105.3, tail averaging 64.4). (Pacific coast dis- 

 trict, from southern California to British Columbia and eastward to 



Montana) Sialia mexicana occidentalis, adult male (p. 155) 



cc. Under parts without chestnut or cinnamomeous (light blue, passing into white 



on alidomen, etc.) (Western North America, fn)m northern Mexico to 



Yukon Territory and Creat Slave Lake.) . . .Sialia arctica, adult male {p. 156) 



bb. Pileum and hindneck brownish gray, grayisli brown, or dull grayish blue. 



(Adult ftmiales.) 



c. Under parts partly cinnamomeous. 



d. Throat cinnamomeous, like chest and sides. {Sialia sialis.) 

 e. Upper parts more bluish, the dorsal region, pileum, and hindneck more 

 or less strongly suffused with l)lue, the back scarcely if at all browner 

 than pileum. 



