NORTH AMERICAN BIRDS. 441 



times sit for hours and warble his soft, agreeable song, with open, 

 quivering wings. Here too, proudly stationed, he surveys the sur- 

 rounding territory and awaits any intruder that may approach, whose 

 presence he resents, and whom he assails with astonishing vigor. 



Dr. J. G. Cooper has aptly said that the Bluebird always bears the 

 National colors, red, white and bluo, and that it is one of the most 

 strikingly peculiar of American singing birds, and in its habits a model 

 of civilized bird life. Its natural nesting places are in the deserted ex- 

 cavations of Woodpeckers, hollows of trees, and even in the crevices of 

 rocky cliffs. With the progress of civilization the Bluebird has taken 

 advantage of modern surroundings, adopting the boxes that are put up 

 for its use, nesting also in every conceivable nook and corner in houses 

 and barns. Very frequently letter boxes upon fences are taken pos- 

 session of. I found a Bluebird's nest in the interior of a wheel of a 

 railroad car during the strike a few years since, and on another occa- 

 sion, in Morrow county, Ohio, I discovered a brood of young Bluebirds 

 in a Cliff Swallow's nest under the eaves of an old barn. 



The normal color of the eggs of the Bluebird is uniform pale blue, 

 unspotted. They are four, five, and sometimes six in number, and 

 their average size is .84X.62. The eggs of this bird are frequently 

 very light bluish-white, and rarely pure white. All found in one nest 

 are of one tint; that is to say, a white egg is never found in a set with 

 the blue ones. Mr. Norris has several sets which are as white as those 

 laid by Woodpeckers. The Azure Bluebird (Sialia sialis azurea Swains) 

 inhabits Southern Arizona and Eastern Mexico. 



767. Sialia mexicana SWAINS. [ 23.] 



'Western Bluebird. 



Hab. Western United States, from the Rocky Mountains to the Pacific, south to Southern Mexico. 



An inhabitant of Western United States north to British Columbia. 

 Its habits are exactly similar to those of the Eastern Bluebird. It 

 nests in holes and cavities of decayed trees, between their trunks and 

 the loose bark, making the nest of sticks, grasses, straws, and almost 

 any rubbish procurable. Mr. Walter E. Bryant states that Dr. Cooper 

 informs him that he has known a Bluebird to build in a Cliff Swal- 

 low's nest. The eggs of this species are four or five in number, uni- 

 form pale blue, of a slightly deeper shade than those of the preceding 

 species, and average .81 x .62. 



768. Sialia arc tica (SWAINS.) [24.] 



Mountain Bluebird. 



Hab. Rocky Mountain region, north to Great Slave Lake, south to Mexico, west to the higher moun- 

 tain ranges along the Pacific. 



Known as the Rocky Mountain and Arctic Bluebird. It is very 

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