FAUNA OF THE ALEUTIAN ISLANDS AND ALASKA PENINSULA 127 



Lagopus mutus chamberlaini 



Chamberlain's rock ptarmigan is known only from Adak Is- 

 land, but it undoubtedly occurs on neighboring islands. It is 

 somewhat grayer than atkhensis, and is darker on the top of the 

 head and upper neck — an effect, not particularly striking, that 

 results from a greater number of black markings. No doubt 

 chamberlaini and atkhensis intergrade on some of the intermedi- 

 ate islands. 



Laing (1925) found rock ptarmigan on Adak "even more nu- 

 merous" than on Atka. He collected five males on Adak, April 13, 

 1924, that had started to molt into summer plumage. The date, 

 like that for the molt into summer plumage by atkhensis, is un- 

 usually early for ptarmigan. 



Lagopus mutus sanfordi 



Sanford's rock ptarmigan is abundant on Kanaga, Tanaga, and 

 neighboring islands. Bent (1932), speaking of Tanaga, says: 

 "The ptarmigan were tamer and more abundant here than on 

 any of the other islands that we visited; we shot more than 40 

 in one afternoon." The two specimens we obtained on Kanaga Is- 

 land are referable to sanfordi, showing that this race occupies 

 Tanaga and Kanaga, at least. 



As Bent said, Sanford's rock ptarmigan is paler than chamber- 

 laini, and is somewhat more ochraceous than either chamberlaini 

 or atkhensis. Bent (1932) says: 



Although I described and named this race myself (1912), in honor of my 

 friend Dr. Leonard C. Sanford, who cooperated with me in organizing our 

 expedition to the Aleutian Islands, I must confess that it is only slightly 

 differentiated from the Adak ptarmigan. We all noticed a difference when 

 our birds were collected, and when we laid our series of about 40 specimens 

 of sanfordi beside nearly as many of chamberlaini, it was easy to see that 

 the Tanaga birds were appreciably paler than the Adak birds. The Tanaga 

 birds are therefore the lightest in color of any of the Aleutian ptarmigan, 

 and have the finest vermiculations. 



Lagopus mutus gabrielsoni 



Gabrielson's rock ptarmigan occurs on Amchitka Island, the 

 type locality, as well as on Little Sitkin Island and Rat Island. 

 We have no specimens from Semisopochnoi Island, where this 

 form may occur also. In 1938, Scheffer obtained, on Amchitka, 

 a specimen whose crop was filled with berries of Empetrum 

 nigrum, no doubt a favorite food of all these rock ptarmigan. 



In summer plumage, the male gabrielsoni differs from sanfordi 



