AUKS. 45 



Order X. ALCIFORMES. 



Family ALCID^E. AUKS. (Plates IV., V.) 



The Auks, Guillemots, Razor-bills and Puffins, included in this family, [Case 24.] 

 form a group of exceptional interest on account of the modifications of 

 structure which they have undergone to adapt them to a purely pelagic 

 life. Though allied to the Gulls and more distantly to the Plovers, they 

 are now superficially very different, and as in the Grebes and Divers the 

 shape and carriage of the body are specially suited to their peculiar 

 habits. Their distribution is confined to the coasts of the North 

 Circumpolar region, none being found either in the tropical zone or in 

 the Southern Hemisphere. Black and white are the predominating 

 colours in the plumage of these birds. They breed generally on rocky 

 cliffs and islands in enormous colonies, make no nest, and the female lays 

 her one or, in some species, two eggs on the bare rock or, as in the case of 

 the Puffins, in a rabbit-burrow or hole tunnelled by the birds themselves. 

 The young are covered with down when hatched, and in their first 

 plumage differ but little from the adult. 



The smallest members of the group are the little Auks, represented 

 on the top shelf of this case by several diminutive species. Least of 

 these is the Minute Auk (Simorhynchus pusillus) (390), remarkable on 

 account of its extremely small bill, while the Pigmy Auk (S. pygmaus) 

 (391) and the Crested Auk (S. cristatellus] (392) have an elongate frontal 

 crest of narrow feathers curving forward over the bill. In these species, 

 as in their allies the Puffins, the supplementary ornamental shields on 

 the bill are cast after the breeding-season, and the bill then appears much 

 smaller and of a dull brown colour. The Perroquet-Auk (Phaleris 

 psittaculus) (393) from the North Pacific is another curious little form, 

 and the Unicorn Puffin (Cerorhyncha monocerata) (394), from the North 

 Pacific and Bering Sea, has a peculiar horny excrescence at the base of 

 the bill during the breeding-season. 



The Common Puffin or Sea-Parrot (Fratercula arctica] (397) [PI. IV.], 

 a common British species, the Horned Puffin (F. corniculata) (396), and 

 their ally the Tufted Puffin (Lunda cirrhata) (395), differ from all the 

 species already mentioned in having the claw on the inner toe very 

 strongly curved. During the breeding-season these birds have the bill 

 brilliantly ornamented, but in autumn a remarkable moult takes place, 

 and the coloured shields fall off, leaving the bill about half its former 

 size. This is clearly illustrated on the tablet exhibited in the Case, 

 where the head of the Common Puffin is shown with the recently cast 

 shields alongside the bill. 



From the coasts and islands of the North Pacific and Bering Sea 



