100 COLYMBID^. 



are concerned, there can be no difficulty in recognizing the 

 two forms. It is, however, less easy to separate the imma- 

 ture birds, unless the sex of the specimen is known, for a 

 young male of C. r/lacialis is as large as a young female of 

 C. adamsi. Both species are said by Mr. E. W. Nelson to 

 be found on the shores of the Arctic and Bering Seas, and the 

 latter, which he considers to have a circumpolar distribution, 

 is also found throughout the North Pacific, visiting Japan in 

 winter ; indeed its range appears to extend along the Arctic 

 coast of Siberia, at least as far as the mouth of the Yenesei, 

 where Mr. Seebohm was told of a species larger than the 

 Black-throated Diver, which frequented the lakes of the 

 * tundras ' and had a ivhite bill. It has moreover been 

 stated that C. adamsi occurs on the coast of Scandinavia ; 

 and an immature Diver, with a thickened and whitened 

 bill, shot on the coast of Suffolk, and belonging to Mr. J. H. 

 Gurney, was exhibited by Mr. Sclater at a meeting of the 

 Zoological Society (P. Z. S. 1859, p. 206), and supposed to 

 be an example of this species ; it must, however, be re- 

 membered that in the young Great Northern Diver the bill 

 is frequently of a pale horn-colour, and, in the male, of large 

 dimensions. 



During their breeding-season the Northern Divers fre- 

 quent islands, in lakes and pools of fresh water, forming a 

 flattened nest of dead herbage, among reeds and flags, from 

 eight or ten yards to a distance of forty yards from the 

 water's edge. The frequent passage of the birds to and 

 from their nest to the water produces a path or track, by 

 which the nest is sometimes discovered. Mr. Proctor thus 

 notices what occurred to him, in reference to this species, 

 on his visit to Iceland : — " It breeds on the lochs of fresh 

 water about a day's journey from My-vatn ; a single egg was 

 deposited on the bare ground, but just out of water-mark, 

 rather under a rugged bank on some broken ground. I was 

 successful in finding two nests. I allowed the single egg to 

 remain in one of them, in the expectation that another egg 

 would be laid to it, but was disappointed. The old bird was 

 very shy, and always left the egg on our approach, when at 



