582 NORTH AMERICAN BIRDS. 



a 1 . 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. (In 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. (Zn 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. Eggs .87 X -65. Hob. 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. 



