The Great Northern Diver — Colymbus Glacialis, Linnæus
During autumn and winter this species is by no means rare along our coasts. It does not remain to breed on any part of Great Britain, but breeds to the north-west in Iceland, Greenland, and North America.
It feeds entirely on fish, and the adults generally keep well out at sea, unless the weather be stormy, so that the individuals that frequent our shores are mostly immature.
In autumn the young bird has the feathers of the back greyish brown with paler margins; under parts whitish. Bill brownish horn colour.
The adult in its breeding dress has the back black, each feather having two square white spots; the head and neck are black with a purplish gloss, except for two crescentic bands on the fore neck, which are longitudinally striped with white and black. After the autumn moult the whole of the upper parts are pale slaty blue, the head and nape dusky grey, chin and throat white. This plumage is, however, worn for an exceedingly short time and is rarely complete, signs of the new breeding dress appearing before all old feathers have been cast.
The winter feathers of the head and neck are downy. Length 30·32 in.; wing 13·14 in.