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. 
The Little Auk 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 Si- 
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 
