536 DIVING BIRDS. 



ised by the under surface of the wing being grey, instead of smoky white. The 

 typical form of this species has a large white wing-patch : but there are two 

 varieties (carbo and motzfeldi), severally distinguished by the presence or absence 

 of white on the head, in which the wing is uniformly black on the outer side. 



All the guillemots are very similar in their mode of life, being essentially 

 oceanic birds, which only visit the rocks during the breeding-season, and are only 

 found inland when driven there by stress of weather ; while they are markedly 

 sociable and gregarious. Their food consists of fish, supplemented by various 

 crustaceans ; the common species being especially partial to the fry of herrings 

 and pilchards, which are captured at night in the open sea. Rapid, though 

 heavy and laboured in its flight, the common guillemot is enabled to reach the 

 summits of almost inaccessible cliffs for the purpose of breeding, where, as in the 

 Fame Islands and at Flamborough, it congregates in myriads. On the ledges of 

 the precipitous cliffs near Bempton another noted breeding-place the guillemots, 

 are sometimes so densely crowded together as to remind one of a swarm of bees. 

 The breeding-season in Britain commences in May and lasts till August; and 

 while the other species agree with the rest of the family in laying but a single 

 egg, the black guillemot deposits two. The eggs may be laid either on the bare 

 ledges of rock or in fissures ; and while at times several may be found together, 

 at other times they lie singly. In coloration, guillemots' eggs are remarkable for 

 their extraordinary variability. According to the writer last-mentioned, "the 

 ground-colours are cream, white, blue, and yellowish green, dark and clear pea- 

 green, and reddish and purplish brown, with every conceivable intermediate tint. 

 Some are irregularly blotched, others are fantastically streaked with browns, 

 pinks, or greys in endless variety, whilst a few are spotless or nearly so." Some 

 closely resemble those of the razorbill, from which they may always be 

 distinguished by appearing creamy -white instead of green when viewed by 

 transmitted light. 



Short-Billed The North Pacific is inhabited by six or seven much smaller 



Guillemots, guillemots, characterised by their very short beaks, of which the tip 

 is not decurved. These constitute the genus Brachyrhamphus, and while in some 

 species, like the marbled guillemot (B. marmoratus), the front of the metatarsus 

 is reticulated, in others, such as the black- throated guillemot (B. antiquus), it is 

 covered in front with large scutes. 



Breeding solely within the limits of the Arctic Circle, the little 

 auk, or rotche (Mergulus alle) is an Atlantic species, which only visits 

 the British Isles in winter, and is even then far more common in the Orkneys and 

 Shetlands than in the south. It is a very small bird, measuring only about 8J 

 inches in length, and differing from all the members of the family by the shortness 

 of the symphysis of the lower mandible, in which the angle of the chin is much 

 nearer to the tip of the beak than to the nostrils, instead of the reverse. The 

 whole beak is shorter than the head, very thick, and broader than high at the 

 base ; the profile being arched, and the tips of both mandibles notched, while the 

 upper one is faintly grooved. The rounded and lateral nostrils are placed at the 

 base of the beak and partially covered with feathers. In coloration, the little auk 

 very closely resembles the guillemot ; the head, chin, and throat, as well as the 



