THE PRINCIPAL BIRD GROUPS 89 



deep laterally compressed coulter - shaped bill 

 of the typical Auks, and the short arched bill 

 of the Little Auk, and lastly the still more 

 laterally compressed and deeper bill of the 

 Puffins, with its wonderful series of horny 

 sheaths or appendages, assumed during the 

 breeding season and lost in autumn (conf. 

 p. 28). The Auks are all pelagic birds, and 

 as a rule only resort to the land to breed. 

 They are more or less gregarious at all seasons, 

 but especially so during the time of repro- 

 duction, when they congregate at certain time- 

 honoured spots to rear their young. They 

 are comparatively silent birds, their notes 

 being harsh and grunting. Their principal 

 food is fish and small marine animals. The 

 Guillemots and Auks make no nest, but lay 

 their one, or in exceptional cases two eggs 

 either on the rock ledges or in chinks and 

 fissures ; the Puffins usually burrow into the 

 soft ground or select a suitable crevice amongst 

 cliffs or even masonry, and form a rude nest 

 of dry grass, at the end of which they lay 

 one egg, exceptionally two. The eggs of the 

 Auks and Guillemots are almost without excep- 

 tion very handsomely marked, and present 

 such a variety of colour as to render detailed 



