CONCEALED OR COVERED NESTS 103 



accommodation, are scattered over most parts of the 

 British coast where suitable breeding places occur. 

 The nest, typical of the Pigeons already described in 

 a previous chapter {conf. p. 69), is placed on con- 

 venient ledges, or in chinks and fissures in the sides 

 or roof of the selected cave. The Shag (Phalacro- 

 corax graculus) is another species that prefers a cave 

 for nesting in if one is to be had. Its nest is a bulky 

 structure, placed on some convenient shelf or in a 

 fissure made externally of sticks, dry stalks of plants, 

 and seaweed, and lined with dry grass, straws, and 

 turf, the whole being more or less matted together 

 with droppings and decaying fish refuse. This nest, 

 I should say, is used year after year, and numbers of 

 pairs breed in the same cave if sufficient sites are 

 available. The Cape Petrel, the nest of which we 

 have already mentioned {conf. p. 77), may also be 

 instanced as a breeder in caves or grottoes. 



Coming now to the most typical cave dwellers, we 

 may give as our first instance that curious species, 

 the Cock of the Rock (Rupicola). Several species of 

 these birds are known, inhabitants of the tropical 

 portions of South America. The nest is made of 

 mud, possibly mixed with a sticky saliva, the inner 

 structure composed of twigs, lined with moss, and is 

 attached to the sides of some dark cave. Then we have 

 that extraordinary species, the Oil Bird (Steatornis 

 caripensis), perhaps better known by its Spanish name 

 '• Guacharo," an inhabitant of various parts of South 



