CONCEALED OR COVERED NESTS 97 



for a few feet and then makes a sharp turn to the 

 chamber, or it will follow a horse-shoe shaped curve. 

 The tunnels are about five inches in diameter, and the 

 nest chamber from about a foot to a foot and a half in 

 width. The nest is generally made of dry horse- or 

 cow-dung, this material carpeting the chamber to a 

 depth of several inches, but sometimes a more 

 elaborate structure of dry grass, stalks of plants, and 

 feathers is formed. 



Other remarkable bird burrowers are furnished by 

 the Puffins (Alcid^). The habit of burrowing, how- 

 ever, is by no means universal amongst these 

 birds, some species rearing their young in hollows 

 and crevices of rocks and cliffs. A very typical 

 burrowing example of these birds is the Common 

 Puffin (Fratercida arctica) found breeding in 

 abundance in certain parts of the British Islands. 

 Like most burrowing birds the Puffin occasionally 

 annexes the hole of some other creature, that of a 

 rabbit especially, but in the great majority of 

 instances it is its own architect. This bird burrows 

 into the soft earth on sea-cliffs, as'well as into the level 

 ground, whilst in other cases it finds a convenient 

 shelter in old and ruined masonry. The formidable 

 beak — shaped something like a coulter of a plough — 

 and the excessively sharp claws are both used in the 

 excavation of the burrow. Like the Burrowing Owl, 

 the Puffin casts out the loose earth and stones behind 

 it with its legs and feet, and I have often stood below 



G 



