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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 Limicolz, 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 
strageler. This is the largest of them all, the 
White-billed Diver, Colymdus adamsz, 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 résumé of 
their more salient characteristics, we will now 
proceed to a more detailed examination of their 
economy. 
GREAT NORTHERN DIVER. 
This species, the Colymdbus glaciats of Linnzeus 
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 
