140 BIRDS OF THE COMMANDER ISLANDS. 



scbatkan birds, ami each cue of the stages cau be iuatcbed exactly by 

 specimens from other localities within the extensive range of F. rusti- 

 coins. This remark also apjjlies to the two "nnchal areas" of a color 

 which rfeverzow describes as ^'albotulvescens," but which is evidently 

 too deep in the plate accompanying the memoir. 



In my '-Orn. Expl. Kamtsch.," p. 204, I expresse-^ myself in regard 

 to the Bering Island birds as follows: "My specimens from Bering 

 Island are rather light, however, and may, perhaps, be nearest related 

 to the Greenland race [F. holhceUi], if any average differences exist. 1 

 should, however, be inclined to the belief that in such case the Pacific 

 bird might be entitled to separate recognition. The paucity and small- 

 iiess of the dark spots on the under parts would seem to indicate such 

 a possibility " 



The two additional specimens from Kamtschatka, and Severzow's de- 

 scription of his Bering Island bird, certainly go some way to strengthen 

 the above ''possibility," but, as I have been unable to find a tangible 

 character, I shall wait for more material before deciding. Dr. Severzow 

 finds a positive character in the dusky barring of the under tail-coverts, 

 which he describes as only occupying the outer web in F. grehnitzUiy 

 while in the allied species it is said to occupy both webs. Now, in point 

 of fact, all ray birds have the under tail-coverts nearly uniform white, 

 with only faint traces of streaks (young) or cross-bars (adult), conse- 

 quently still lighter than Severzow's specimen. In a specimen from 

 Nushagakh, and in one from Saint Paul Island, Pribylof group, I find a 

 similar state of things, while in other specimens from the American side 

 of Bering Sea, and also in most of those from the interior of Alaska, the 

 Arctic coast, Greenland, and Iceland, the stripes or bars are more or 

 less heavy, though very variable even in birds from the same locality 

 and of apparently corresponding age. But the exceptions are too 

 numerous and the variation too great to establish even an average 

 difference. Thus I have before me an adult bird from Disco, Green- 

 land (No. 95127), which has the under tail-coverts colored precisely as 

 described by Severzow in F. grehnitz'kii. Another (Xo. 79016), an adult 

 female collected by Governor Feucker, at Godhavu, Greenland, has 

 only a very few and small dusky marks. A young bird from the same 

 country (No. 5G051) has only the shafts dusky, and an adult male (No. 

 51689)* from the Yukon River, near the month of the Porcupine River, 

 Alaska, has only faint traces of dusky m the outer webs. 



Should future accumulation of additional material prove that the 

 Kamtschatkan bird (including part of the specimens trom Alaska) never 

 have the lower tail-coverts so decidedly barred with dusky as the ma- 

 jority of the American specimens, then it might become a profitable 

 question to discuss whether such a form should correctly stand as Falco 



*Tbis is the specimen which served Mr. Kidgway as the type of his Falco gyrfalco 

 var. sacer (FORSTER),iu Baird, Brewer, aud Kidgway, Hist. North Am. Birds, III, p. 

 115 (1675). 



