78 BIRDS' NESTS 



the former, selecting cavities or grottoes in the 

 rough cliffs for the purpose. In these it forms a 

 simple hollow, and there lays its egg upon no lining 

 whatever. It is interesting to remark, however, that 

 birds sitting in these hollows, with no egg or chick 

 beneath them, have been noticed placing little stones 

 around them with their bills, as if impelled by some 

 almost lost impulse to gather something with which 

 to make a nest. I have also remarked a very similar 

 proceeding on the part of the Fulmar Petrel {conf. 

 p. 43). This latter bird must also be classed as a crude 

 nest-builder, many individuals contenting themselves 

 by hollowing out the soil on the cliffs into a basin- 

 like receptacle, which is generally scantily lined with 

 dry grass. Then the (Estrelata pai'virostris, breeding 

 on Christmas Island, makes no nest, but deposits its 

 egg in a hole scooped in the bare ground, under a 

 low bush. 



Although a few of the Gulls and Terns (Lariformes) 

 make somewhat elaborate nests, these birds, as a 

 group, fairly come within the limits of the present 

 chapter. The crudest nest-builders are unquestion- 

 ably the Terns. Indeed some of these birds, as we 

 have already seen, make no provision whatever for 

 their eggs, laying them on the bare sand or shingle ; 

 others content themselves with the merest apology 

 for a procreant cradle. This usually takes the form 

 of a saucer-like hollow, either amongst herbage or 

 on pebbles and shingle above high-water mark, round 



