MOUNTAIN CHICKADEE 363 



The nest is made of soft mosses and the fur and hair of mammals, 

 being warmly lined with finer material of the same kind, much like the 

 nests of other chickadees. 



Eggs. — The mountain chickadee seems to lay very large sets. Sets 

 of less than six are probably incomplete; and from that the numbers 

 run up to 12, sets of 9 being- common. There are 16 sets of eggs of 

 this chickadee in the collection of the University of Colorado Museum; 

 m this series there are three sets of 7, seven sets of 9, three sets of 10, 

 two sets of 11, and one set of 12 eggs. 



The eggs are normally ovate in shape, with variations toward rounded- 

 ovate. The shell is smooth and practically lacking in gloss. The ground 

 c.olor is pure, dead white, with much variation in the extent of the 

 markings. In most sets a small or a large proportion of the eggs are 

 entirely unmarked; and in some sets all the eggs are spotless pure 

 white. Some eggs are faintly marked all over the entire surface with fine 

 dots of pale or reddish brown. In others these small spots are more 

 or less concentrated about the larger end. An occasional set is bril- 

 liantly marked with a ring of bright reddish brown or orange-rufous spots 

 or small blotches. 



The measurements of 40 eggs average 15.6 by 12.3 millimeters; the 

 eggs showing the four extremes measure 16.5 by 12.9, and 13.8 by 11.5 

 millimeters. 



Young. — I have no information on the period of incubation for this 

 race. 



Dean Amadon has sent me the following note on a nestful of young 

 mountain chickadees that he observed at 9,800 feet on the east slope of 

 Snowy Range, Medicine Bow Mountains, Wyo., about 20 feet from 

 the ground in a natural crevice of a large lodgepole pine : "Both parents 

 were feeding the young very frequently at the time, which was 7 p.m., 

 just before dark. Once, when the two parents appeared with food at 

 the same time, they crouched on limbs near the nest, opening and quiv- 

 ering their wings, as do young birds when begging for food. The 

 young were noisy enough to be heard for about 30 feet from the nest 

 tree; I was told that they had left the nest and v/ere not seen two 

 days later, on July 8. Nest was in rather dense pine stand, but only 

 40 feet from the clearing made by a main road." 



Claude T. Barnes tells me that five tiny fledgings, in a nest that 

 he examined, "hissed in the manner of a snake" when he reflected light 

 into the nest. The nest was in a quaking aspen, which, "twisted by 

 winds and snow, had cracked, making a cozy hole about 4 inches deep 

 and 3 inches in diameter." 



Flunm-ges. — Tn the juvenal plumage, young birds are much like adults. 



