126 BRITISH SEA BIRDS. 
web-footed birds, with no hind toe, with the 
legs placed far back, and the bill subject to 
great variation in size, and in some _ species 
presenting considerable change in appearance 
according to season. All the Auks have com- 
paratively short and narrow wings; in the recently 
extinct Great Auk these were incapable of support- 
ing the bird in the air; and the tail is remarkably 
short, in some species being scarcely perceptible 
under ordinary circumstances. The Auks are 
exclusively confined to the north temperate and 
polar regions of the Northern Hemisphere: and 
by far the greater number of species inhabit 
the Northern Pacific. They number some thirty 
species. The prevailing colours of the Auks 
are black and white; none of them are showy 
birds; but some species are remarkable for their 
eccentric nuptial plumes, and for the brilliancy 
of colour of the bill, The Auks are thoroughly 
aquatic, and not adapted in any way for a 
terrestrial existence. They swim well, dive with 
marvellous skill, and save during the incubation 
period, pass most of their time on the sea. 
None of the species are remarkable for any 
great migration flights; as a rule they wander 
little from their high northern homes. They are 
all gregarious birds, breeding in companies wherever 
possible. Some species undergo but little change 
in their appearance between summer or winter 
plumage; others are more remarkable in this 
