124 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



and, on the extreme western end of the chain, Attu Island. It is 

 represented by eight subspecies : neUoni, yunaskensis, atkhensis, 

 chamberlaini, sanfordi, gabrielsoni, toivnsendi, and evermanni. 



As reported elsewhere (Murie 1944, p. 122), the rock ptar- 

 migan of the Aleutian Islands-Alaska Peninsula district fall into 

 two groups: A dark, more or less blackish group (in summer 

 plumage) , and a yellowish group (also in summer plumage) . The 

 dark group, comprising nelsoni, yunaskensis, and evermanni, oc- 

 cupies the Alaska Peninsula and the eastern Aleutians as far 

 west as Yunaska, with the representative subspecies evermanni 

 on the extreme western end of the chain, Attu Island. The yellow- 

 ish group, comprising the other five forms, occupies the middle 

 and western Aleutians from Atka Island as far west as Kiska. 



The five so-called yellowish ptarmigan races in the middle 

 Aleutians are actually very similar in appearance and are hard to 

 distinguish without a series for comparison purposes. The fact 

 that so many forms can be separated within such a comparatively 

 limited area can be explained only by the partial isolation af- 

 forded by island habitat, though a given race is not necessarily 

 confined to a single island, but may occupy a group of islands. 



Close knit as these five "yellowish" races are, it is still possible 

 to separate them. The three eastern forms, atkhensis, chamber- 

 laini, and sanfordi (the most difficult to distinguish one from an- 

 other), form a group characterized by pale coloration, and, more 

 particularly, by finer barring in the plumage. The two western 

 forms, gabrielsoni and townsendi, have much heavier barring. 



As Bent has pointed out, middle-Aleutian ptarmigan occupy 

 lowland areas, comparatively speaking, in contrast with the high- 

 mountain habitat of rock ptarmigan farther east. This does not 

 mean that the middle-Aleutian races avoid highlands; they oc- 

 cur on relatively high ground on Atka and Kiska, and elsewhere. 

 But the terrain of these islands is not particularly rugged, nor 

 of the high-mountain type. Amchitka, for instance, is a low is- 

 land. It is true, as Bent has said, that these rock ptarmigan live 

 to a large extent in grassy areas, but it does not necessarily fol- 

 low that they have responded directly to environment by taking 

 on colors that blend with the color of dead grass. This is a 

 possibility, but at present we do not have sufficient facts for a 

 conclusive decision. 



Lagopus mutus nelsoni 



Nelson's rock ptarmigan is a dark race that occurs throughout 

 the Alaska Peninsula area, including Kodiak and Afognak is- 



