264 



Sierra Club Bulletin. 



of desirable nesting sites around human habitations has^ 

 in at least one instance, caused the Mountain Bluebird 

 to forsake its alpine breeding-ground for levels at which 

 its does not ordinarily breed. 



There can be no doubt that in the Sierra Nevada 

 Sialia aretica is a true mountaineer. They are most abun- 

 dant from an altitude of 9,000 to 11,000 feet. There one 

 may see them, as in the accompanying photographs, con- 

 ducting their housekeeping in woodpecker holes or hol- 

 low trees. There they hover, like great azure butterflies, 

 over the luscious green of alpine meadows. And Ridg- 

 way reports that he saw them on the heights, sporting 

 with apparent delight among the snowflakes of on- 

 coming winter storms, when other birds were seeking 

 shelter in cozy copses. Severe climatic changes, however, 

 usually start them on their vertical migration to the lower 

 valleys. 



On the floor of the Hetch Hetchy Valley and in sim- 

 ilar localities of the transition zone, up to the Murray 

 pine meadows, the Western Wood Pewee (Myiochanes 

 ricJiardsonii) was found breeding in considerable num- 

 bers. It wears a livery of dark grayish brown above, 

 shading on the under parts into whitish or pale yellow- 

 ish, washed with dark gray. The Wood Pewee has the 

 alert appearance and many of the actions of a small fly- 

 catcher. Its quiet call, a liquid tweer, uttered from its 

 perch on the dry branch of a tree as it watches for in- 

 sects, lingers long in a Sierran camper's memory of tran- 

 quil noon hours in sunny woodlands. The trout angler is 

 apt to find the Wood Pewee's nest while casting along the 

 banks of streams where black cottonwoods (Populus 

 trichocarpa) and white alders (Alnus rhombifolia) stand 

 guard against ranks of yellow pines and incense cedars. 

 In every case I found the nest saddled on the horizontal 

 branch of a tree, at heights varying from eight to twenty 

 feet, and usually above the water. They were, of course, 

 found also in other situations, but most often along the 

 streamxS. 



