MOUNTAIN CHICKADEE 577 



be seen while perched on a twig to pound with his bill on the part of the 

 wood between his feet, producing an intermittent tattoo audible for some 

 distance. This possible exhibition of 'spring vigor,' recalls the much 

 louder, rolling tattoo which the flicker and certain other woodpeckers are 

 wont to beat in the spring. 



Nesting activities among the Mountain Chickadees are commenced in 

 late April or early May. After the pairs separate off from the winter 

 flocks, the two mates go about in close companionship and begin inspection 

 of old woodpecker holes and of natural cavities either in living trees or 

 in dead and weathered stubs. The nest holes of the White-headed Wood- 

 pecker abound in a good part of the chickadee's range, and it is to this 

 bird more than to any other one agency that the chickadee is indebted 

 for suitable nesting places. The White-head digs a new nest hole for itself 

 each season, and as the cavities persist for several years in condition 

 suitable for use by chickadees the latter may even have opportunity for 

 exercising choice. Indeed the chickadees do investigate many holes before 

 settling upon one as the location for the nest of the season. The manner 

 of the birds' work in gathering material was not observed. By the time 

 the nest is ready for eggs there has been accumulated a felted mass of 

 soft material some five to six inches below the entrance. This material 

 consists chiefly of hair. In some nests the soft hair of chipmunks is the 

 principal material, while in others the coarser hair of the Mule Deer 

 predominates. In one nest examined at Porcupine Flat there was hair 

 from meadow mouse, California Ground Squirrel, and chipmunk. In 

 another nest we found down feathers of some bird; and in still another, 

 bones of small mammals were mixed with the hair in such a manner as 

 to suggest that the chickadees had chanced upon some owl pellets and used 

 parts of these in building. 



The material composing the nest is closely compacted so as to make 

 a thick felt carpet, and as such, must be of considerable value in conserving 

 warmth when the female chickadee begins to incubate her relatively large 

 clutch of eggs. In some instances this 'carpet' rests directly upon the layer 

 of small chips which served as flooring for the woodpecker tenants of an 

 earlier year. But if the hole is unusually deep, grass and similar coarse 

 material is piled in first so that the nest proper will not be too far below 

 the entrance. 



The number of eggs varies, 5 and 8 being the extremes for the com- 

 plete sets found by us ; probably 7 is the most usual number. During the 

 period of incubation, which lasts about 2 weeks, the female occupies herself 

 almost or quite exclusively in covering the eggs. The male, on the other 

 hand, continues to forage actively, and may be seen to visit the nest from 

 time to time, supplying food to his mate. Confirmation of this division 



