of Colymbus adamsi in Norivay. 276 



older), and it appears as if the summer-plumage of these 

 older and mature individuals were retained longer into the 

 autumn than that of the somewhat younger birds in their 

 first summer-plumage. 



The third winter -plumage. — The last summer-feathers of 

 these birds are first changed towards the close of the winter. 

 One specimen in the Tromso Museum, shot in Kvalsund, 

 near Tromso, on the 11th January, 1893, still retains a 

 number of white-spotted summer-feathers on its back and 

 shoulders. The rest of the plumage belongs, therefore, to 

 the new (third) winter-plumage, which is, on the whole, like 

 that of the winter-plumage of the second year, but the upper 

 rump-feathers and the tail-coverts want the narrow light 

 margins, i. e. the remains of the young plumage, which are 

 to be found, more or less defined, in the two-year-old birds. 

 The grey winter-feathers are produced by the throwing off" 

 of the margins of the summer-feathers up to the white spots. 

 These lose their colour, and form the same greyish-white 

 patches inside the margin as are described in the winter- 

 plumage of the second year. 



The pure winter-plumage of the third year is probably 

 borne for only a short time, as the white-spotted feathers of 

 the summer plumage soon begin to appear. 



Distinctness of the species. — Recent observations liave made 

 it probable that C. adamsi forms a species distinct from 

 C.glacialis, being of East-Arctic [" Pacifico-glacial,^' Palmeti) 

 origin, whilst C glacialis is diff'used over the West-Arctic 

 area. The individuals which arrive on the Norwegian coasts 

 (and shores of the North Sea) during the winter come pro- 

 bably from Siberia, where they appear to be found in summer 

 from Behring Strait to the districts of Yenisei and Taimur- 

 land {Seebohm, Middendorff) . This species was found by 

 the 'Vega'' Expedition (187!)) breeding in Tschuktschi- 

 land, near Kamtschatka, and a sitting female and its eggs 

 were obtained, the only instance yet recorded of its breeding 

 in the Old World (Palmen, 'Vega' Exped. Results, vol. v. 

 p. 403) . 



During the autumn migration a number of individuals 



