BIRDS OF NORTH AND MIDDLE AMERICA. 607 



nearly circular, in the anterior end of the very broad and anteriorly 

 rounded nasal fossae. Rictal bristles inconspicuous. Wing long- (about 

 four times as long as tarsus or a little more), rather pointed (four 

 outermost primaries longest, the ninth longer than tifth); primaries 

 exceeding secondaries b}" length of tarsus or a little more. Tail about 

 three-fourths as long as wing, slightly rounded or nearl}' even, the 

 rectrices rounded at ends, more than half hidden by the upper coverts. 

 Tarsus about as long as middle toe with clasv; outer claw reachino- 

 about to base of middle claw, the inner not quite so far; hind claw 

 much shorter than its digit. 



QoJor.s. — Adult male blue with chestnut or tawny wing-bands; adult 

 female and young brown (paler ])elow) without distinct streaks, the 

 wings with one or two bands of tawny. 



The genus Guiraca^ as properl}' restricted, includes but one known 

 species, G. cceruJt((, with a southwestern and a southern Mexican 

 suV)species. 



Range. — Lower Sonoran Province of United States and southward 

 over Mexican plateau to highlands of Chiapas (in winter to Cuba and 

 Nicaragua). (Monotypic. ) 



KEY TO THE SPECIES AXD SUBSPECIES OF GUIRACA. 



a. Smaller (wing averaging SH.06 in male, 81.53 in female; tail averaging 66.04 in 

 male, 62.48 in female) ; coloration darker, with wing-bands narrower. (Eastern 

 United States; south in winter to Cuba and Yucatan.) 



Guiraca caerulea caerulea (p. 607) 



aa. Larger (wing averaging 90.42 or more in male, 84.58 or more in female; tail 



averaging 70.36 or more in male, 66.55 or more in female); coloration lighter, 



with broader wing-bands. 



b. Smaller (wing averaging 90.42 in male, 84.58 in female; tail averaging 70.36 in 



male, 66.55 in female; exposed culmen averaging 15.75 in male and female; 



depth of bill averaging 13.46 in male and female; tarsus averaging 20.32 in 



male, 20.83 in female). (Southwestern United States and plateau of Mesico; 



south to western Nicaragua in winter.) Guiraca cserulea lazula (p. 610) 



hh. Larger (wing averaging 89.92, tail 71.12, exposed culmen 18.80, depth of bill at 

 base 15.49, tarsus 22.35 in female; male not seen). (Highlands of western 

 Chiapas, southern Mexico. ) Guiraca caerulea chiapensis ( p. 612) 



GUIRACA CffiRULEA CiERULEA ^Linnaeus). 

 BLUE GROSBEAK. 



Adult male in summer. — Uniform, slightly glossy, dull ultramarine 

 blue, the feathers of the back more or less dusky centrally; a narrow 

 black capistrum, involving the lores, anterior margin of the forehead 

 (at least laterally), extreme anterior portion of malar region, and chin; 

 wings and tail blackish with dull bluish edgings, the middle wing- 

 coverts with most of the exposed portion chestnut or cinnamon-rufous 



