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.
THE WHITE-BILLED NORTHERN DIVER
Colymbus adamsi, G. R. Grey
This species breeds in the Far North, wandering south in winter; two or three examples have been taken on our shores, and it is probable that owing to its resemblance to the preceding species it has been often overlooked.
The chief characteristic is the bill, which is yellowish white at all seasons, and the lower mandible is also markedly upturned. The white streaks on the transverse throat bands are much fewer in number than in the preceding species. Length about 33 in.; wing 15·1 in.
THE BLACK-THROATED DIVER
Colymbus arcticus, Linnæus
The Black-throated Diver is very rare in England, and the few examples that are obtained are usually immature. In Ireland it has only been taken at long intervals, but in Scotland it breeds locally throughout the north and west.