476 THRUSHES, SOLITAIRES, BLUEBIRDS, ETC. 



Nest. In holes in trees, stumps, posts, or bird-boxes ; made largely of 

 dried grasses. Eggs : 4 to 7, plain pale greenish blue. 



Food. Largely caterpillars, grasshoppers, and crickets ; also wild ber- 

 ries, like hackberry and woodbine. 



The eastern bluebird ranges west to the base of the Rocky Moun- 

 tains, being a rare summer resident in Colorado. 



766a. S. S. azurea Baird. AZURE BLUEBIRD. 



Similar to sialis, but sides of neck brown, and under parts less ruddy 

 brown ; upper parts sometimes greenish blue, suggesting arctica. Length : 

 6.40-7.10. Male: wing 4.05-4.20, tail 2.70-2.95, bill .47-.50. Female: 

 wing 3.90, tail 2.55. 



Distribution. Southern Arizona and Mexico. 



767. Sialia mexicana occidentalis (Towns.). WESTERN BLUE- 



BIRD. 



Adult male. Upper parts dark purplish blue and chestnut ; throat pur- 

 plish blue; breast dark rufous; rest of under parts mixed brown, dull 

 purplish and gray. Adult female : head, neck, and upper parts gray, washed 

 with brown on back; rump and tail bright blue; outside tail feathers 

 edged with white. Young : like young of sialis, but bill slenderer. Male : 

 length 6.50-7.12, wing 3.95-4.45, tail 2.62-3.05, bill .45-.50. Female: 

 wing about 4, tail 2.50. 



Distribution. Breeds in Transition zone of the Pacific coast, from Brit- 

 ish Columbia to Calif oraia. and east to western Nevada and Idaho ; casu- 

 ally during migrations to New Mexico. 



Nest. In woodpecker hole high in a pine or other tree and also in 

 bird -houses. Eggs: (1 set) 6, pale blue. 



Food. Largely caterpillars ; also crickets, weevils, ants, moths, locusts, 

 and grapes in winter months when insect food is less abundant. 



The western bluebird'is often seen on roadside fences from which 

 it flies down to pick up insects. In the pine woods it sits close to the 

 tree trunks on short broken-off branches. It has the soft warble of 

 its kind, and the delicate bluebird way of lifting the wings while 

 perching. 



76 7a. S. m. foairdi Ridgw. CHESTNUT-BACKED BLUEBIRD. 



Similar to occidentalis, but back wholly chestnut. 



Distribution. Transition and Canadian zones of the Rocky Mountain 

 district, south to Arizona, Texas, and northwestern Mexico. 



Food. Partly grasshoppers, weevils, crickets, and sumac berries. 



The chestnut-backed bluebird extends east as far as Pueblo, Colo- 

 rado, during migration, and breeds from the base of the foothills 

 up to 9500 feet. 



768. Sialia arctica Swains. MOUNTAIN BLUEBIRD. 



Adult male. Upper parts light purplish blue or greenish blue ; under 

 parts pale greenish blue. In winter color dulled by dull brownish tips to 

 feathers above and below. Adult female : upper parts brownish gray, wings 

 and tail bright blue ; under parts fawn color, with blue showing through. 



