ORNITHOLOGICAL EXPLORATIOKS. 195 



1 consider myself excusable in making the mistake of calling this 

 bird Lagopus albvSj when I wrote my preliminary report on the islands, 

 although it really belongs to the Attagen- group, so differently colored 

 is it from all other Eock-ptarmigans. Of course, if I had looked closer 

 at the structural characters, such an error could not have happened, but 

 the specimens were not at hand when I wrote my report, and the general 

 color, in connection with the statement of Prof. W. H. Dall (Notes 

 on the Avifauna of the Aleutian Islands, especially those west of Una- 

 lashka, 1874, p. 5) that L. albus is the only species of grouse found on. 

 the Aleutian Islands,* led me to make such a blunder. As soon as I 

 got winter specimens the mistake was plain, but I never dreamed of a 

 new species of ptarmigan before it came to actual comparison of speci- 

 mens. 



It seems from the blackish prejestival plumage of this species, espe- 

 cially the almost uniform blackish prsBpectus, that it is more nearly al- 

 lied to L. muta than to L. rupestris, in spite of its brown color j but it is 

 a perfectly good species and affbids a most interesting proof of the pa- 

 laiarctic relationship of the Commander Islands on the one hand, and of 

 their remarkable isolated zoological position on the other. It would 

 almost seem as if the isolation, as a factor in the development of new spe- 

 cies or forms, is effective in inverse projjortion to the size of the isolated 

 area. The ptarmigans of Europe have been separated from each other 

 on three or four different mountain systems, probably as far back as the 

 end of the Glacial period. Still the difference between L. mutus from 

 Scandinavia andL. mutus vulgaris from Southern Europe is rather slight. 

 It is at present hardly possible to tell how long a time has elapsed since 

 the Commander Islands have been separated from the mainland ; but, 

 even if that took place still earlier, the distinctness of many of the 

 birds appears very remarkable. 



Before entering on a more detailed comparison with allied forms, 

 some remarks upon the changes of plumage among these birds may not 

 be out of place. 



In my preliminary report (p. 74), I concluded " that no marked sea- 

 sonal plumage can be distinguished, except the white plumage of the 

 winter and the dark one of the summer," for the reason that these birds 



* It now turns out that the species inhabiting the American islands of the Aleutian 

 Chain belong to two different races, L. rupeHtris nelsoni Stejn., and L. riqjestris atkhensia 

 (Turner), and that alha does not occur at all on the islands. It is first on the Shuma- 

 gin Islands that alha is found. I have myself examined a $ in breeding plumage ob- 

 tained by Dr. T. Bean on Unga. 



