360 bULLETlN 191, UNITED S'iAl£S NATIONAL MUSEUM 



Mrs. Wheclock (1904) gives the period of incubation as 14 days. 

 She says that the young remained in the nest nearly three weeks, 

 which seems to be an unusually long time for such small birds; and for 

 fully two weeks longer they were begging to be fed. She observed 

 that "the nestlings were fed by regurgitation until four days old, when 

 fresh food was given." 



Food. — Strangely enough, nothing specific seems to have been pub- 

 lished on the food of any of the races of the mountain chickadee; if 

 there has, I have been unable to find it. But its feeding habits are simi- 

 lar to those of the other chickadees ; it has repeatedly been observed 

 examining the twigs, foliage, and crevices in the bark of trees, where 

 it doubtless finds a variety of insect food; and it is fair to assume that 

 its food does not differ very materially from that of other members of 

 the genus. Grinnell and Storer (1924) have seen one thoroughly ex- 

 amining the interior of a rotted-out cavity, where it probably found in- 

 sect food of some kind. 



Behavior. — Grinnell, Dixon, and Linsdale (1930) describe in some 

 detail the intimidation behavior of this species when the nest is in- 

 vaded : 



When a slab of rotten wood was removed the bird lunged, at the same time 

 spreading its wings convulsively, and then gave a prolonged hissing sound — just 

 that order of procedure. The bird repeated this performance nineteen times by 

 count before it suddenly flew from the nest at the close approach and light touch 

 of the observer's hand. The body had been kept closely depressed into the nest 

 cavity. The lunges were rather inane — the bird simply struck out, in one di- 

 rection and then another. At the moment of the lunge, the black-and-white 

 striping of the head brought her into abrupt and conspicuous view of the observer 

 peering into the cavity — reinforcing the surprise effect of the sounds produced. At 

 times, the hissing soiuid was produced, tlic wall of the cavity was struck, and the 

 white of the head moved, all at the same instant. * ♦ * During the winter chicka- 

 dees regularly made up portions of the companies of birds of several species that 

 foraged together through the day. Some of the individuals that moved to low 

 altitudes in winter joined circulating bands of bush-tits. 



Grinnell and Storer (1924) write: "After the nesting season the 

 chickadees and several others of the smaller birds are wont to associate 

 with one another in flocks of varying size. Such a gathering was seen 

 in Yosemite Valley on July 30, 1915. Included in the openly formed 

 yet coherent aggregation were the following species: Mountain Chicka- 

 dee, Black-throated Gray \\''arbler, Western Chipping Sparrow, Sierra 

 Creepers, Warbling Vireo, and Cassin \'ireo. The birds were foraging 

 through black oaks, incense cedars, and young yellow pines, each kind 

 of bird of course adhering to its own particular niche and own method 

 of getting food." 



