206 



SEA-BIRDS 



piclilis 



Fig. 36 

 Breeding distribution of four cormorants: Double-crested cormorant 

 Phalacrocorax auritus; Mexican cormorant, P. olivaceus; Shag, P. aristo- 

 telis; Red-cormorant, Halietor africanus 



The nest, built by both sexes, is usually of marine materials; 

 seaweed, flotsam, etc. Cormorants collect heather and sticks from 

 cliffs near the nesting site. Gannets fly together to grassy slopes whence 

 they tear off* and convey vegetation to the gannetry (Ailsa Craig, 

 Grassholm). Boobies and man-o'-war birds, building in trees, steal 

 twigs from neighbours' nests, and gannets rob each other in like manner. 



Little is known about the pairing of the gannet; probably forma- 

 tion of the love-bond is a slow process, beginning with the meeting 

 of inexperienced young adults late in the summer at the gannetry; 



