MOUNTAIN BLUEBIRD (Sialia currucoides) 



The male mountain bluebird is a striking bird with sky-blue or azure plum- 

 age and light underparts. The female is a dull brownish-gray with a 

 touch of blue on the rump, tail and wings. The Pima Indians believed that 

 the mountain bluebird was originally an unlovely gray, but that it acquired 

 its present exquisite azure coat by bathing in a certain lake of blue water 

 that had neither inlet nor outlet. The distribution and abundance of blue- 

 birds in Yellowstone and Grand Teton is apparently influenced to some 

 degree by the availability of nesting sites which are largely confined to 

 dead trees in forest clearings. Lightning fires, epidemics of wood-boring 

 insects, and similar natural agents, including the drowning or scalding of 

 trees by hydrothermal features, are therefore beneficial to the species. 

 The mountain bluebird is generally common in both Yellowstone and 

 Grand Teton. 



Townsend's Solitaire Dale & Marian Zimmerman 



WARBLING VIREO (Vireo gilvus) 



The warbling vireo is a plain, sluggish dweller of the forest canopy. Show- 

 ing a decided preference for decidous trees, the warbling vireo is more 

 easily detected by song than by sight. The song is a repetitious, rolling 

 warble. The male sings incessantly throughout the summer. The warbling 

 vireo may be distinguished from other small residents of the forest canopy 

 by the heavy bill and the lack of wing bars. Vireos feed almost exclusively 

 on insects. They are especially fond of small caterpillars and measuring 

 worms. The nest of the warbling vireo is a neat, compact cup composed 

 of bark fibers, fine grasses, and plant stalks, ornamented with spider egg 

 cases, lichens, and cottonwood down. The nest is usually attached to the 

 fork of two branches, high in a deciduous tree. The tree most commonly 

 used for nesting in Yellowstone and Grand Teton is the narrow-leaf cot- 

 tonwood. 



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