COLYiMBID/E. 695 



THE WHITE-BILLED NORTHERN DIVER. 



CoLYMiius ADAMSi, G. R. (Iray. 



This Diver is the Arctic representative of the preceding species, 

 from which it differs in several important particulars. The bill, which 

 is yellowish-white at all seasons, is deeper and has the under mandible 

 remarkably upcurved from the angle ; the head and upper neck are 

 glossed with green, while the lower neck is tinged with purple (the 

 reverse being the arrangement in the (ireat Northern Diver) ; the 

 streaks on the upper throat-band are only 6 in number, with lo on 

 the lower one ; the white spots on the scapulars are larger — while 

 those on the flanks and upper tail-coverts are smaller — than in the 

 sub-Arctic species ; and linally, this high northern form is superior 

 in size. Early in the spring of 1852 an example, which is now 

 in the collection of Mr. J. H. Gurney, was shot at Pakefield near 

 Lowestoft, and the late Dr. Churchill Babington has figured an im- 

 mature specimen in his ' Birds of Suffolk,' believed to be from that 

 county ; while one in winter-plumage, in the Museum at Newcastle, 

 was certainly shot on the Northumbrian coast, according to Mr. John 

 Hancock. Some of the distinctive features of this species had 

 attracted the attention of the late Sir James Clark Ross, who 

 virtually discovered this bird on Boothia in 1S30, though Gray only 

 named it in 1859 ; but until Mr. Seebohm worked out and summar- 

 ized the points of difference (Zool. 1884, p. 140), its claims to 

 recognition were somewhat coldly received. Other examples have 

 doubtless been overlooked ; and an unusually large bird with while 

 mandibles, shot by Mr. E. T. Booth on Hickling Broad in December 

 1872, may have belonged to this species. 



During the breeding-season the White-billed Diver appears to be 

 circumpolar in its distribution. It is probably this large species— 

 and not C. gladalis—ili^t is found on the island of Jan Mayen, and 

 has been observed in Si)itsbergen, Novaya Zemlya, and Arctic 

 Russia generally. In Asiatic Siberia it was described to Mr. See- 

 bohm by the natives as frequenting the tundra lakes on the Yenesei, 

 and Dr. von Middendorff states that the Divers he obtained on the 

 Taimyr peninsula had yellowish-white bills ; while eastward it can 

 be traced to Bering Sea and its islands, and to Alaska. In the 



