92 Unwersity of California Publications in Zoology [Vol. 30 



In young birds, too, the first "winter plumage, preliminary" is 

 only partly acquired. Over the whole of the lower parts below the 

 upper breast the molt is direct from the juvenal to the white winter 

 plumage. On the head, neck, and dorsum, the "first winter, pre- 

 liminary" is partly acquired, but white feathers appear on the chin 

 and throat long before the juvenal plumage is lost on back and flanks. 

 Young birds of alexandrae at hand (Willett coll.), taken in October, 

 are in ' ' first winter, preliminary, ' ' almost complete. There are but a 

 few juvenal feathers left to distinguish young from old. In every case, 

 though, young birds and adults may be distii^uished by the differently 

 shaped tertials, which linger longer than almost any other feathers of 

 the brown-colored plumages. 



On September 1, adults from the Atlin region had almost all 

 acquired new flight feathers and rectrices. In the young, the juvenal 

 rectrices are lost at a very early age, before the bird is half grown, 

 being almost the first of that plumage to go. On September 1 nearly 

 all young birds seen had completely acquired the black rectrices of 

 the first winter plumage, slightly narrower than in adults but not 

 otherwise different. 



To summarize these details of plumage, they all go to show the 

 incomplete nature of the "winter plumage, preliminary," inserted 

 between the breeding plumage and the white winter plumage in adults, 

 between the juvenal plumage and white winter plumage in young 

 birds. Judging from material at hand it is less perfectly acquired at 

 the northern limit of the range of the willow ptarmigan, and more 

 perfectly acquired toward the southern limit, where longer summers 

 give more time before the white winter plumage" is essential. On the 

 islands of southeastern Alaska, the habitat of Lagopus I. alexandrae, a 

 region of relatively mild winters, the "winter plumage, preliminary" 

 is acquired more nearly to perfection than perhaps anywhere else in 

 the general range of the species. As a result of the perfect acquisition 

 of this plumage in this particular dark-colored race, we see fall birds 

 that closely resemble the Scotch red grouse (as described above), which 

 bird, of course, is a southern species of Lagopus which does not acquire 

 a white winter plumage at all. 



In this account of the plumage variations of the several subspecies 

 of the willow ptarmigan here under consideration I have used through- 

 out the terminology employed by Dwight (1900, p. 147) in his exposi- 

 tion of the seasonal and other changes undergone by these birds. My 

 own observations (made much easier through a previous reading of 



