238 BULLETIN 16 2, UNITED STATES NATIONAL MUSEUM 



before the postjuvenal molt into the late summer plumage begins. 

 This is similar to the preliminary winter, or tutelar, plumage of 

 adults. About a month later, in September, the molt into the pure- 

 white winter plumage begins. These two molts effect a complete 

 ehange of plumage between August and October, except that the two 

 outer primaries are retained for a year, which serve to distinguish 

 young birds from adults. 



What little material is available seems to indicate that the molts 

 and plumages of adults are similar to those of other ptarmigan. A 

 partial prenuptial molt of the contour plumage, head, neck, and 

 back takes places from March to June. The late summer, or tutelar, 

 plumage is assumed by a partial postnuptial molt beginning late in 

 July; this is much grayer, more finely vermiculated, and with less 

 black than the nuptial plumage, which is more heavily vermiculated, 

 with more black spots, on a more " ochraceous-buff " ground color. 

 Females are more buffy or ochraceous than males in both plumages. 

 A supplementary molt produces, in September and October, the 

 complete change into the pure-white winter plumage. 



Food. — Dr. Sylvester D. Judd (1905a) summarizes the food of this 

 ptarmigan, as follows : 



During winter in Colorado, according to Professor Cooke, they subsist, like 

 '>ther ptarmigan, largely on willow buds. The stomachs of two birds collected 

 at Summitville, Colo., in January, 1891, at an altitude of 13,000 feet, were found 

 to contain bud twigs from one-third to one-half inch long, but the kind of bush 

 from which they came could not be determined. Doctor Coues, quoting T. M. 

 Trippe, states that the food of this bird is insects, leguminous flowers, and the 

 buds and leaves of pines and firs. According to Major Bendire, the flowers and 

 leaves of marsh marigold (Caltha leptosepala) and the leaf buds and catkins 

 of the dwarf birch (Betula glantiulosa) are eaten. Dr. A. K. Fisher examined 

 the stomachs of two downy chicks collected on Mount Rainier, Washington, and 

 lound beetles and flowers of heather (Cassiope mertensiana) and those of a 

 small blueberry. 



Mrs. Bailey (1928) adds: 



The crop of one New Mexico specimen was filled mainly with leaves of 

 the dwarf willow, and fruiting spikes of Polygonum viviparum, with one flower 

 of Geum rossii, while the gizzard held mainly Polygonum seeds, a few other 

 small seeds, a few small grasshoppers, and other small insects. 



Behavior. — Quoting Trippe, Coues (1874) writes: 



In localities where it is seldom molested it is very tame, and I have been 

 informed by persons whose word is worthy of belief, that they have fre- 

 quently killed it with sticks. But when persistently persecuted, it soon be- 

 comes wild, and leaves the range of a shot-gun with surprising quickness. 

 After hunting several large flocks for three or four days, they grew so shy 

 that it was difficult to approach within gunshot, although at first they had 

 been comparatively tame. Nimble of foot, the Ptarmigan frequently prefers to 

 run away on the approach of danger, rather than take wing, running over 

 the rocks and leaping from point to point with great agility, stopping every 



