208 BULLETIN 162, UNITED STATES NATIONAL MUSEUM 



In adult males the black lores are complete and in some old females 

 there are traces of them. 



In the far north, where the ground is not wholly free from snow, 

 the prenuptial molt, in both young and old birds, is much delayed 

 and is more or less incomplete, as the short arctic summer gives 

 hardly time for the birds to acquire and shed the summer and 

 autumn plumages. But farther south, where the birds live on a 

 wholly bare ground, the molt of the body plumage is more com- 

 plete, and the sexes become distinguishable in plumage, as the birds 

 are now practically adult. In this and subsequent nuptial plumages 

 the males assume a coarsely vermiculated and mottled dress of gray- 

 ish buff and dusk}^, except that the wings, tail, abdomen, and feet 

 remain as in winter. The females make a more extensive molt, 

 becoming coarsely mottled and barred with buff and black, but 

 retaining the white remiges, white belly, and black rectrices. 



Soon after this nuptial, or summer, plumage is acquired, the molt 

 into the autumn plumage begins, which helps to make the complete 

 molt into the white winter plumage. The autumn plumage is much 

 like that of the young bird and is very finely vermiculated in both 

 sexes, instead of coarsely vermiculated or barred, as in summer. The 

 sexes are now much alike again. These two plumages are well 

 illustrated in the colored plates published by A. L. V. Manniche 

 (1910). 



Food. — In summer the food of the rock ptarmigan includes a 

 number of insects, but it is made up more largely of leaves, buds, and 

 berries, such as crowberries, whortleberries, bearberries, and the ten- 

 der leaves and buds of birches and willows. Numerous seeds are 

 eaten, as well as sphagnum and other mosses, and the leaves of Lab- 

 rador-tea. In winter, when food is scarce, they have to feed on buds 

 and twigs and the seeds of such weeds as they find above the snow. 

 Their long, strong claws, which are highly developed in winter, 

 enable them to dig down through the snow to reach the mosses and 

 such of the above plants as they can find. 



Behavior. — Turner says in his notes : 



Their flight is rapid, and when flying with a stiff wind they require the 

 quickest shot to stop them. The beat of the wing is so rapid that it is scarcely 

 discernible, and when the bird is sailing the somewhat decurved wings are 

 held almost motionless as it rolls from side to side. The direction of flight 

 is always in a straight line, rising only sufficiently to clear a patch of trees or 

 intervening ridge, the latter at times passed over only by a few inches in height, 

 to the plain or valley beyond. Sometimes they will fly more than a mile 

 before alighting and at other times only a few rods, depending altogether on 

 the character of the weather. If it is a cold, blustering day with much snow 

 drifting or falling, these birds dislike to take flight, and by using a slight 

 amount of discretion the birds of an entire flock may be all secured, but if 

 it is calm and cold, or warm, they take flight and at this time are rarely 



