200 SEA-BIRDS 



The food and fishing methods of the gannets have been well 

 described by Gurney (191 3), who concludes that the deeper the fish 

 are swimming the higher the altitude from which the gannet's plunge 

 is made. He records that the Belfast fishermen are thereby guided as 

 to the depths at which to set their nets. There is generally a mistaken 

 notion that the gannet dives in order to gain impetus and strength 

 to spear its prey; and the story is handed down of how trawler hands tie 

 a fi.sh on to a piece of floating wood so as to deceive the gannet, which 

 is killed by the impact of its dive upon the board, or else — more 

 popular report still — its bill is embedded in the wood. These tales 

 are largely without foundation in fact; one trawlerman told us that 

 every time he tried this experiment of tying a fish to a board and trailing 

 it astern when gannets were present, the fish was devoured by other 

 birds which alighted beside the floating wood. The gannet does not 

 spear the fish: the dive is for the purpose of gaining depth and velocity 

 under water in order to attack a fish or shoal from beneath^ and the 

 fish is seized in the open bill as the bird rises to the surface. It is usually 

 swallowed under water, unless it is large; gannets are sometimes 

 attacked and pursued in the air by skuas, and boobies are chased by 

 man-o'-war birds; and it is probably from fear of these and of fellow- 

 competitors (Kay, 1948) that the gannet and booby swallow as much 

 of their fish-food as possible under water. Having done so, however 

 they are by no means free from the air attacks of the skuas (great, 

 arctic and pomarine skuas are recorded as attacking the gannet), 

 and man-o'-war birds, which will often pursue them until they are 

 forced to disgorge. Some skuas, particularly the great skua, will 

 tenaciously follow a gannet which has been feeding, and several reliable 

 observers have reported that the skua has grabbed the tail of the gannet 

 in its determination to force the gannet to throw up. 



It is true that gannets and brown pelicans dive from various heights, 

 according to the depths at which fish-prey are swimming (for this 

 purpose their binocular vision must be functionally important) but 

 records of their reaching great depths in their dives are not sub- 

 stantiated. Pelicans make shallow dives, and often do not submerge 

 completely. Gannets are said to be able to dive to thirty fathoms (180 

 feet) on the evidence that they have been caught in nets set for fish 

 at these depths. Anyone who has seen gannets diving when a herring- 

 net or a trawl is being brought to the surface at sea will realise that it 

 is during the somewhat slow process of hauling, when the net is floating 

 near or at the surface, filled with fish, that the gannet is attracted by 



