582 NORTH AMERICAN BIRDS. 
a’, Breast, etc. fine light greenish blue (in adult male) or brownish gray or 
grayish brown (in female), the belly and under tail-coverts pure white. 
Adult male: Above rich, glossy cerulean-blue, the wings and tail more 
azure, or cobalt; beneath lighter cerulean-blue, the belly and under tail- 
coverts white. (Jn winter, the blue of head, neck, back, and breast ob- 
scured by grayish brown tips to the feathers.) Length 6.50-7.90, wing 
4.60-4.80, tail 3.00-3.15. Adult female: Above brownish gray, the pri- 
maries dull light blue, the rump, upper tail-coverts, and tail brighter 
greenish blue; beneath light grayish brown, the belly and under tail- 
coverts white; a whitish orbital ring. (Jn winter colors deeper, espe- 
cially on lower parts.) Length 7.00-7.20, wing about 4.25, tail 2.75-2.90, 
Young: Quills and tail-feathers as in adults ; above grayish brown, the 
back usually streaked with white; beneath grayish white, the breast 
and sides mottled with grayish brown. Hggs .87 X .65. Hab. Rocky 
Mountain district, north to Great Slave Lake, south into Mexico; west 
across Great Basin, to higher ranges along Pacific coast. 
768. S. arctica Swains. Mountain Bluebird. 
