The large single white egg being laid, both birds take their turn at incubation, and invariably sit with their head facing the entrance, and woe betide any one who by mistake enters the wrong hole, for their beaks are exceeding sharp and powerful, and they cling on with all the tenacity of a bull-dog. They feed chiefly by night and spend the day resting on the water or at the mouth of their burrows. The food consists of small fry, and when feeding their young as many as three or four fish are caught and carried up in their bill at the same time. If approached by boat, they remain till one is just on them, and then suddenly dive. Under the water their progress is extremely rapid, and both wings and feet are brought into play, but especially the former. The young are clad in very thick long down of a dark smoke-grey colour. As they grow they will often move about the passage, running to the entrance and meeting their parents, but never venturing outside, while if they meet another young one bound on a similar errand a stern fight ensues. Not, however, till they are fully fledged do they leave the burrow and then immediately take to the water, on which they are quite at home, swimming and diving with ease from the very first. The parents, whose plumage has lately been showing signs of wear, now commence to moult, and shed at the same time the ornate sheath at the base of the bill and over the eye, while the beak itself becomes dark and the rosette at the corners of the mouth shrinks. A few more days and by the end of August they have gone—where? They are never seen, and the only evidence of their existence is the occasional occurrence of a dead or starving individual washed ashore or blown inland by a winter’s gale. The head, nape, and the whole of the upper parts and a broad collar round the throat are black. Scales of the head and under parts white. Legs deep orange. Bill chiefly red and orange. The young resemble the parents, except that the beak is much smaller and the legs are pale flesh-coloured. The mode of growth of their wings is quite distinct from that of the Guillemot, the primaries being grown simultaneously with the rest of the plumage. Length 13 in.; wing 6 in. 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.