MOUNTAIN CHICKADEE 575 



winter at any station in the western foothill country. The birds are as 

 fixed in this respect as the Plain Titmouse is in its range. 



During the winter season individual chickadees are not closely restricted 

 as to immediate neighborhood, the birds being then associated in bands 

 which rove through the woods for considerable distances in their daily 

 search for food. But in summer the forage range of individuals is 

 restricted to a small area which has for its center the site chosen for, or 

 occupied by, the nest. Chickadees forage at various heights in the trees, 

 sometimes at 6 feet or less from the ground, again at 50 feet or even higher. 

 On several occasions chickadees have been seen to descend to the surface 

 of the ground and to forage there for a time ; but the birds then hop about 

 with seeming awkwardness, as if out of their proper niche. 



The chickadee population is greatest in the Canadian Zone. Only a 

 few of the birds are found in the Transition Zone and but moderate num- 

 bers occur in the Hudsonian. During June, 1915, before the young were 

 abroad, our censuses in Indian Caiion and at Porcupine Flat gave between 

 2 and 3 of these birds per hour of observation. A 4-hour census in 

 Yosemite Valley on May 31, 1915, revealed only 2 birds, and the same 

 number were noted during a similar trip there on April 28, 1916. In 

 the Hudsonian Zone, between Young Lake and Tuolumne Meadows, 8 were 

 recorded in 4 hours on July 9, 1915. But by the end of July young were 

 out everywhere and "the woods were full of chickadees." No less than 

 36 were counted in 3I/2 hours by one of us going from Tenaya Lake to 

 Mirror Lake on July 31, 1915. 



Mountain Chickadees are sociable creatures and spend most of their 

 time in small flocks. The individuals comprising these flocks are con- 

 tinually calling, with the probable purpose of keeping within hearing 

 distance of one another. The company travels along intact, yet spread 

 out through adjacent trees, so that the individuals do not cover each 

 other's ground in their search for food. Apprehension of danger by one 

 is at once communicated to all members of the company, so that each may 

 be instantly on the alert. In the spring, by the end of April if not earlier, 

 these bands break up and pairs are formed as a first step in the nesting 

 program. When the young are fledged enough to leave the nest the family, 

 both parents and young, goes forth and remains as a group at least until 

 time for the fall molt. In early autumn flocks numbering 10 to a dozen 

 individuals are formed, and in this manner the chickadees spend the time 

 until the impulse comes to prepare for nesting once more. 



In Yosemite Valley on April 30, 1916, a pair of Mountain Chickadees 

 was followed for about twenty minutes as the birds flew from tree to tree 

 gleaning insect food of various sorts. Black oaks seemed to be preferred 

 and the birds would explore one tree fairly well before going on to another. 



