34 NESTS AND EGGS OF BIRDS. 



pail' had taken jDOSsession of a white -bellied swallow's nest-, and 

 had actually covered up the swallow's two eggs with their grass 

 bed. The unspotted eggs are slightly deeper in their pale blue 

 than those of S. sialis^ which they also excel in size, measuring 

 .^"j by .69 of an inch on the average. But the differences, if 

 any, between the eggs of kS. sialis and this and the following 

 species, are not such as would appear in an engi'aving ; and I 

 have therefore omitted figures of eggs of the two latter. Two 

 broods are said to be brought out, the first being hatched very 

 early 



18. THE ROCKY MOUNTAIN BLUEBIRD. 

 SI ALIA ARCTIC A S'.vainson. 



The home of this bird is among the ridges and open table-lands 

 of the whole length of the Rocky Mountains^ where it is not un- 

 common from 7,000 feet upward, during the bi'eeding season. 

 It resembles its eastern and western congeners in all partic- 

 ulars. In May and early June it builds its nest, choosing some 

 deserted woodpecker's hole, a hollow limb, a hole in the rocks, 

 a bank, or the shaft of a mine ; and is gradually adapting itself 

 to civilized accommodations. An insignificant bed of dry grass 

 constitutes the nest, and four to six eggs are laid, which average 

 about .85 by .63 of an inch, and are not with certainty to be 

 distinguished from those of the other species. Capt. Bendire 

 observes that there is much variation in their color in Oregon, 

 some being of much brighter tint than others. Two broods are 

 raised annually. Both parents feed the young, and exhibit 

 great anxiety for their safety, chirping and uttering a plaintive 

 cry. In the north, after the close of the breeding season, 

 these bluebirds assemble in flocks to feed on the open plains. 



