370 BRITISH BIRDS. 



Genus ALCA. 



The Auks were placed by Linnseus partly in the genus Colymbus and 

 partly in the genus Alca. The latter is recognized in the twelfth edition 

 of the ' Systema Naturae' (i. p. 210). The Razorbill, A. tor da (being the 

 Alca alca of Brisson), is the type. 



The Auks may at once be distinguished from the Puffins by their nostrils. 

 In the former genus the feathers at the base of the bill encroach on 

 the nostrils, often partly concealing them ; in the latter genus there is 

 always a bare space on the bill between the feathers and the nostrils, and 

 the bill is provided with orange- red sheaths, which are deciduous in 

 autumn. 



There are only twelve species of Auks, but one or two of them are divi- 

 sible into subspecies. The genus may be regarded as circumpolar, but 

 some of the species are confined to the Pacific coasts of the Arctic regions. 

 Seven species are European, all of which either breed on our shores or are 

 visitors in winter or on migration. 



The Auks are thoroughly maritime in their habits, frequenting the open 

 sea, only visiting the rock-bound coasts to breed. They are more or less 

 gregarious at all times of the year, and breed in large colonies. They 

 swim and dive with great ease, but on the land walk clumsily and, when 

 perched, usually sit on the tarsi as well as the feet. Their food consists 

 principally of small fish and fry, crustaceans and mollusks. They are very 

 silent birds, and their only note is a guttural sound. They make no nest, 

 but lay their eggs, which only in the Black Guillemots exceed one, in 

 crevices of the rocks or on ledges. Their eggs are remarkably handsome 

 and vary considerably in colour and form. 



