40J. BRITISH BIRDS. 



Botli sexes take it in turns to sit on the eggs. Two is tlie usual number, 

 and it is doubtful if more are ever laid. They vary in ground-colour from 

 olive-brown to russet-brown, and are somewhat sparingly spotted with 

 black. The spots vary in size from that of a pea downwards, and are 

 generally most numerous round the larger end. The underlying spots 

 are much paler and are not very numerous. The eggs vary in length from 

 3 8 to S-4< inch, and in breadth from 2'4 to 2*1 inch. The smaller eggs 

 are indistinguishable from large eggs of the Black-throated Diver. 



The Great Northern Diver is generally a very silent bird, but at its 

 breeding-grounds its cries are often heard, and, like those of its allies, 

 resemble the screams of tortured children ; they sound very weird, and 

 can be heard at a great distance over the water. Like its congeners, this 

 Diver feeds almost exclusively on fish, which its unrivalled powers of 

 diving enable it readily to procure. As soon as the young are able to fly, 

 the breeding-grounds are deserted for the nearest sea-coast, where they 

 are tended for some time by their parents. 



The Great Northern Diver is a large bird, as big as a Goose, though 

 more slender. The colour of the sexes is alike, but the female is slightly 

 smaller in size. In nuptial plumage it almost exactly resembles the Black- 

 throated Diver below the neck, except that the uniform feathers on the 

 upper parts are also covered with small white spots like the wing-coverts. 

 The head and neck are black, glossed with purple on the chin, upper 

 throat, sides of the head, crown, nape, and hind neck, and with green on 

 the lower throat and sides of the neck. Across the middle of the upper 

 throat is a row of about a dozen short white streaks, and on each side of 

 the neck a row of longer white streaks, of which there are about eighteen 

 on each side. Bill black ; legs and feet greenish black ; iridcs crimson. 

 After the autumn moult a plumage is assumed which can scarcely be dis- 

 tinguished from that of the Black-throated Diver at the same season of the 

 year, nor can the two species be distinguished in young in first plumage, 

 except by size. The dimensions of the wing overlap that of the Great 

 Northern Diver, varying from 15 to 13 inches, and those of the Black- 

 throated Diver from 13j to 12 inches ; the depth of the bill at the nostril 

 is a more reliable character, measuring in the former species from TO to 

 •9 inch, and in the latter from '8 to '7 inch. Young in down are blackish 

 brown on the upper parts, paler brown on the underparts. 



