DIVERS, GREBES, AND CORMORANTS. 155 



colour as in adults. Whether the vernal change in 

 colour is effected without moulting, as in the Auks 

 and some of the Limicolae, appears not to have yet 

 been ascertained. All the species of Divers are 

 visitors to the British Islands, but only two breed 

 in them, and one is an exceptionally irregular 

 straggler. This is the largest of them all, the 

 White-billed Diver, Colymbus adamsi, and a species 

 apparently circumpolar in its distribution. The 

 Divers are all birds of the north-temperate or 

 Arctic regions, during summer ; in winter their 

 range is much more extended, almost reaching to 

 the northern tropics. With this brief resume" of 

 their more salient characteristics, we will now 

 proceed to a more detailed examination of their 

 economy. 



GREAT NORTHERN DIVER. 



This species, the Colymbus glacialis of Linnaeus 

 and of ornithologists generally, is, in its breeding 

 plumage, one of the handsomest of British birds. 

 Its chief characteristics are its large size about 

 that of a Goose black head and neck, double 

 semi-collars of white and black vertical stripes, and 

 black upper parts, marked with white spots of 

 varying size, and arranged in a series of belts. 

 Whether it actually breeds within our limits has not 

 yet been absolutely determined, although evidence 

 is forthcoming that seems to point to the fact. 

 Unfortunately for the seaside student of bird life, 

 the Great Northern Diver is only known as a 



