MOUNTAIN BLUEBIRD 279 



In addition to the more normal nesting sites in all kinds of cavities 

 in various kinds of trees, in holes in banks, in old woodpecker holes, 

 and in the more recently adopted bird boxes, mountain bluebirds' 

 nests have been found in crevices in clifl's and among rocks, in old 

 nests, and in almost any available cavity about human habitations 

 and ranches. Miss Catherine A. Hurlbutt says in her notes: "I once 

 observed these birds carrying nesting material into a cliff swallow's 

 nest under the eaves of a barn, evidently appropriated from the right- 

 ful owners, as there were swallows in all the surrounding nests; also 

 another in a chipmunk hole in the bank of a road cut about a couple 

 of feet above the surface of the road. I am not sure that the young 

 were successfully raised in either nest." 



According to Mrs. Wheelock (1904) both male and female cooperate 

 in building the nest. The materials used are quite varied ; almost any 

 available material seems to satisfy them. K,. C. Tate (1926) lists the 

 following material in Oklahoma nests: "Stems of wild oats, rosin 

 weeds, goldenrod, sticktights and milkweeds, and rootlets of prickly 

 pears, stinking sumac, scrub oak and ticke-grass." And the Macouns 

 (1909) say that a nest found in a clay butte at Medicine Lodge, Sas- 

 katchewan, "was wholly composed of the outer bark of the old stems 

 of Bigelovia graveolens, a composite plant that grew in profusion near 

 the site of the nest. It contained seven light blue eggs. Another nest 

 taken under the same conditions along Frenchman river, Sask., on 

 June 21st, was built of the outer bark of sage brush (Artemisia cana)." 



Eggs. — The mountain bluebird lays four to eight eggs to a set. 

 Five and six are the commonest numbers, and sets of seven are not 

 extremely rare. They are usually ovate and are somewhat glossy. 

 The color is pale blue or bluish white, averaging paler than those of 

 other bluebirds; very rarely they are pure white, much less often than 

 those of the eastern bluebird. They are apparently always unmarked. 

 The measurements of 50 eggs in the United States] National Museum 

 average 21.9 by 16.6 millimeters; the eggs showing the four extremes 

 measure 24.9 by 16.8, 21.8 by 17.8, and 19.8 by 15.2 millimeters. 



Young. — Mrs. Wheelock (1904) writes: 



Fourteen days are required for incubation, and in this the male often, but not 

 always, shares. When not on the nest himself he brings food to his mate, calling 

 to her in sweetest tones from the outside before entering the doorway. The newly 

 hatched young are of the usual naked pinkish gray type, looking as like tiny new- 

 born mice as birds. On the second day down begins to appear in thin hairs on 

 head and back; on the fourth or fifth day the eyes show signs of opening; on the 

 sixth day they open, and the down is well spread over the bodies. 



Up to this time they have been fed by regurgitation, the adult swallowing each 

 bit first to moisten or crush it; but from the fourth day on fresh food is given 

 occasionally, and from the sixth or seventh day all the food given is in the fresh 



