Fam. I. COLYMBIDAE.–_Colymbus septentrionalis_, the Red-throated Diver of the Arctic and sub-Arctic parts of both worlds, is brownish black in summer, with white under-parts and white specks above; the head and neck are lead-coloured, except the nape, which is black with white streaks, and the mid-throat, which is reddish-chestnut. _C. arcticus_, the Black-throated Diver, found in the same regions though with a different distribution, as for instance in Scotland, is blacker, with white bars as well as spots; the crown and hind neck being ashy grey, the sides of the latter striped with black and white, and the throat purplish-black, interrupted by a semi-collar of white with vertical black lines. _C. pacificus_ of western North America is barely separable. _C. glacialis_, the Great Northern Diver, has a much more restricted range, breeding in Iceland, Greenland, and the Fur Countries as far west as the Great Slave Lake, where it meets _C. adamsi_ (hardly differing except in the yellowish-white bill), which extends thence to Northern Asia, and possibly to Spitsbergen and Jan Mayen. The former is black above, with belts of white spots making a "chess-board" pattern; the lower surface is {51}white, and the throat is crossed by two bands of white with longitudinal black bars, while the head and neck are black with a purplish gloss, changing to green below. In winter most Divers are found down to the northern tropic, at which season the throat becomes white, as it is in the young, in which the feathers of the upper parts are duller with whitish edges. The sexes are similar; the bill is normally black, and the feet are bluish or greenish grey. The downy chicks are sooty above. [Illustration: FIG. 15.–Great Northern Diver. _Colymbus glacialis._ × ⅛.]