ROCK PTARMIGAN 207 



Plumages. — The newly hatched chick of the rock ptarmigan is 

 much like that of the willow ptarmigan but is usually somewhat paler 

 and grayer. The crown patch is " chocolate," mixed with and 

 heavily bordered by black; the rest of the head, neck, and breast 

 is " cream-buff " or " chamois," shading off to " colonial buff " on the 

 chin and underparts; a spot on the forehead, a rictal stripe, and a 

 broad auricular stripe are black, the remaining upper parts are 

 heavily blotched and banded with black, " chamois," " honey yellow," 

 and " tawny." 



The juvenal plumage begins to appear almost immediately, the 

 wings coining first, in which the two outer primaries on each wing are 

 white; these white, juvenal primaries are retained all through the 

 first year. Young birds reach the flight stage before they are half 

 grown. In the full juvenal plumage the young birds are darker, 

 more heavily barred, and have less rufous than in the same stage of 

 the willow ptarmigan. The sexes are alike. The entire upper parts 

 are variegated with black, brownish black, " ochraceous-buff," " ochra- 

 ceous-tawny," and white; the feathers are mainly black, tipped, 

 barred, edged, or notched with the buffs ; many feathers in the mantle 

 have a terminal white spot ; the breast and flanks are from " cinnamon- 

 buff " to " pinkish buff," fading out to whitish on the chin and belly, 

 spotted on the chin, throat, and neck, and barred on the breast and 

 flanks with sepia or dusky. About the end of July the molt into the 

 autumn plumage begins ; this is also called the tutelar or preliminary 

 winter plumage; it is common to both young and adult birds and is 

 a transition plumage between the summer and the white winter 

 plumages. The molts overlap and feathers of all three plumages are 

 often seen in the same bird. During August and September the 

 birds are molting almost continuously. The colored body feathers of 

 both young and adult birds in this autumn plumage are much alike 

 and are quite different from the feathers of the juvenal or summer 

 adult plumages, being more finely vermiculated or sprinkled, less 

 heavily barred, and therefore lighter in effect. The black tail feathers 

 are acquired at this postjuvenal molt, which is nearly complete, and, 

 according to Dr. Jonathan Dwight (1900), "the wings (except the 

 median coverts and inner remiges) become white together with the 

 abdominal wedge of the ventral tract and all posterior to it including 

 the flanks, legs and feet; while the head, throat, breast, sides and 

 back become more or less dusky 7 according to the extent of the renewal 

 in different individuals and probably according to the latitude." 



From this time on the colored feathers are gradually replaced by 

 white feathers, until the full, first winter plumage is acquired by 

 this supplementary molt. This is wholly white except for the black 

 rectrices, and in some young males there are traces of black lores. 



