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. The site chosen for the nest is usually an islet in some large loch, and the eggs, two in number, are olive brown, sparsely spotted with black and brown. The young when first hatched are of a uniform smoky grey-brown. In its habits it closely resembles the next species. In summer the back is black, spotted with white, but the spots are not so uniformly distributed as in the former species. Crown and hind neck ash grey, chin and throat black, margined with short black and white stripes and a small band of similar stripes towards the upper end of the patch. Under parts white. The sexes are alike, but the females are slightly smaller. After the autumn moult the chin and throat are white and the upper parts ash brown. The young bird resembles the young of the Great Northern Diver, but is much smaller and the neck is greyer. Length 27 in.; wing 11·75 in. THE RED-THROATED DIVER Colymbus septentrionalis, Linnæus This species is the commonest of the Divers and may be found along all our coasts during the winter months. In the breeding season, except for a few pairs that may still be found on some of the Irish loughs, it is restricted to Scotland so far as our islands are concerned.