126 NORTH AMERICAN FAUNA 61, FISH AND WILDLIFE SERVICE 



than nelsoni, it seems to be more nearly .allied to this darker 

 group to the east. Although its range is thought to be confined 

 to Yunaska, this is not certain. 



Lagopus mutus atkhensis 



Atka: A-gha-de-gach, or A-gha-de-gah 

 Agdlkax (Jochelson) 



Although native names seem to apply to rock ptarmigan in 

 general, it seems appropriate to apply the Atka dialect name to 

 this form found on Atka Island. Turner's rock ptarmigan may 

 possibly occur on Amlia Island (separated from Atka by only 

 a narrow pass), though no specimens were collected on Amlia. 

 Whether this form occurs eastward as far as Seguam is unknown, 

 but it is logical to assume that it does. It may be expected that 

 atkhensis also occurs westward to the next group of islands, and 

 that it intergrades with the neighboring form, chamberlaini, of 

 Adak. 



One is struck by the grayish color of atkhensis, even in flight, 

 as compared with nelsoni. This color is generally more rufescent 

 than chamberlaini, though both birds have the characteristic 

 variegation of gray and rufescent patches. In fact, atkhensis and 

 chamberlaini are hard to distinguish, though, when a good series 

 of each is laid out for comparison, the difference can be seen. 



On April 4, 1924, Laing obtained a series of 15 birds on Atka — 

 a few of these birds were still in full white plumage. The birds 

 were just beginning to molt into summer dress, a change that 

 appears to be slightly earlier in atkhensis than in nelsoni on 

 Unimak Island. 



Rock ptarmigan have always been abundant on Atka, as many 

 visiting collectors have testified. They are able to maintain their 

 numbers in spite of the blue foxes. It was on Great Sitkin — a 

 neighboring island — that I obtained the only direct evidence of 

 cyclic behaviour among the Aleutian ptarmigan. John Taylor, who 

 had a lease on Great Sitkin to raise blue foxes, said that he had 

 placed 14 foxes on the island in 1934. At that time ptarmigan 

 were numerous — "Thousands of them" was the way he expressed 

 it. When Taylor returned to Great Sitkin the following year, 

 ptarmigan were scarce. He did not think that the blue foxes on 

 this large island could have been responsible for such a swift 

 and marked decrease. There had been red foxes on the island 

 before the planting of the blues. This sudden decrease in the 

 ptarmigan population appears to have been a case of the char- 

 acteristic "die-off" of ptarmigan. Similar fluctuations were not 

 reported for Atka Island. 



