HABITS OF THE WESTERN BLUEBIRD 81 



9 , and youug : The changes of phiniage of this species are precisely coin- 

 cident with those of the Eastern Bluebird, and therefore need not be repeated. 

 Immature birds may be recognized, at any rate in the great majority of 

 instances, by traces at least of difference in color between the middle of the 

 back and the other i^pper parts, and between the color of the throat and of 

 the breast. But probably very young birds in the streaky stage could not 

 be determined with certainty if the locality were unknown. 



In some adult males, the dorsal patch is much restricted, or even broken 

 into two scapular patches with continuous blue between ; and similarly the 

 chestnut of the breast sometimes divides, permitting connection of the blue 

 of the throat and belly. Specimens with little trace of the dorsal patch are 

 with some difficulty distinguished from tho-se samples of .S^. siaUs in which 

 there is much blue on the throat — the grayish-blue of the belly, instead of 

 pure white, being, in fact, a principal character. The two species are evi- 

 dently very closely related. 



THIS is the most abundant and characteristic species of the 

 genus in the Colorado Basin. There would appear, how- 

 ever, to be some peculiarity in its local distribution, since, ac- 

 cording to both Mr. Ridgway aod Mr. Henshaw, it has not been 

 seen in Utah. As I stated in the " Birds of the Northwest", 

 certain observations ren<ler it probable that, from the general 

 winter resorts of the species in Arizona and Xew Mexico, it 

 migrates northward along two routes, one the main chain of 

 the wooded Rocky Mountains, the other the Pacific slopes, the 

 Great Basin being thus passed by on either side. Such specialty 

 of movement, however, may be rather apparent than real, and 

 further observations are desirable. The species is resident in 

 most parts of the Colorado Basin, only disappearing for a short 

 time in midwinter from northerly and highly alpine localities. 

 At Carson City, in Nevada, Mr. Ridgway did not see it from 

 the early part of December until the third week in February, 

 when it became numerous. In comparing it with the Rocky 

 Mountain Bluebird, he remarks that, though the two species 

 are associated in winter, they are .sehlom seen together in sum- 

 mer, since the arctica retires to the higher regions to breed, 

 while the mexicana remains in the lower districts, amorjg the cot- 

 ton woods of the river valleys and the scattered pines skirting 

 the foothills of the Sierra Nevada. This corresponds well with 

 my observations made at Fort Whipple, Ariz., where mexicana 

 i.s resident and extremely abundant, though arctica is rather 

 uncommon, and was noticed only in fall and winter. The local 

 distribution may be further elucidated from Mr. Henshaw's 

 observations : — " In Colorado, it seems to be rather uncommon 

 in the eastern part of the Territory. It was not found in June 



6 B c 



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