1926] Swarth: Birds and Mammals from the Ailin Region 91 



willow ptarmigan frequented the floor of this valley and the lower 

 slopes of the surrounding mountains. Their preferred habitat was 

 a tangle of low willow and birch brush, with grassy open patches at 

 intervals. None was seen on the higher ridges or the slopes higher 

 than about 4000 feet ; there this species was replaced by the rock and 

 the white-tailed ptarmigans. 



On September 1, a trip was made to "Blue Canon," a local name 

 for a section of upper Spruce Creek some twelve to fifteen miles south- 

 east of Atlin. Willow ptarmigan were then beginning to gather in 

 large flocks. In the valley bottom relatively few birds were seen, 

 though some were scattered all through this section, too; the center 

 of abundance was on the lower slopes of the mountains, at from 3500 

 to 4000 feet. This was above the more extensive tangles of willow and 

 trailing birch, and was a much more open sort of country. Thickets of 

 dwarfed balsam, and some of willow and birch, were interspersed with 

 open stretches, grass-covered or carpeted with Empetrum and other 

 low-growing shrubs. 



Willow ptarmigan, in flocks of from ten or twelve (single families, 

 presumably) up to sixty or seventy, were within sight or hearing prac- 

 tically all of the time that we remained at that level. The larger 

 flocks were, I was told, the first indication of much greater gatherings 

 that were assembled during the winter months. On this date (Sep- 

 tember 1) specimens were taken of adults and young of both sexes. 



Adult males taken in midsummer (June 30) in the breeding 

 plumage retained a great deal of white on the belly, and these old 

 white feathers apparently remain until replaced by white feathers at 

 the end of August. Adult males taken September 1 are mostly white 

 on the lower breast and abdomen. Adult females are mostly in the 

 reddish "winter plumage, preliminary," to use the descriptive phrase 

 originating with D wight (1900), though always with many barred 

 feathers of the breeding plumage persisting on breast and flanks, 

 and some blackish feathers of the same plumage on the back. Over 

 the whole belly the molt in every specimen examined was direct 

 from the barred breeding plumage to white winter garb. There is an 

 adult female of alexandrae at hand (Willett coll.. Prince of Wales 

 Island, Alaska, September 23, 1919) in the reddish post-breeding 

 plumage, with but a few scattered barred feathers left. I have seen 

 none from the interior that has assumed this plumage so nearly in its 

 entirety. In the Atlin region it is evident that the white winter 

 plumage begins to come in before the reddish "winter plumage, 

 preliminary" is more than half acquired. 



