228 SEA-BIRDS 



and grain may be procured at harvest time; and they follow the plough. 

 Gulls in fact are omnivorous, freely taking vegetable matter where the 

 normal diet of fish and flesh — alive or as carrion — is in short supply. 

 The ivory-gull lives on the droppings of seal, walrus and polar bear 

 all the year round, supplemented with crustaceans, molluscs and insects 

 when these are available (particularly at nesting times). The larger 

 gulls in summer devour the eggs and chicks and even adults of other 

 sea-birds, and often the chicks of their own species. Most gulls work 

 the mud, sand or saturated turf, trampling with both feet until worms 

 or sand-eels appear. The great blackback drops eggs of birds (the pink- 

 footed goose included) from a height to break them, but cannot dis- 

 tinguish between hard and soft ground. Herring-gulls drop small shell- 

 fish (clams, cockles, mussels, and whelk-shells containing hermit- 

 crabs) from a height of not more than about 25 ft., (possibly because 

 of fear of a rival getting to the crushed delicacy first) on rock and sand 

 indifferently, apparently unable to appreciate the greater effectiveness 

 of the rock compared with the sand for crushing the shell. Common 

 gulls do the same. It does not appear to be an instinctive habit, but 

 rather one acquired by a few individuals only; but it is copied by 

 others watching the expert at work. Rooks drop mussels and walnuts 

 in the same manner. It is recorded that a highway bridge in New 

 Jersey, U.S.A., was littered with the remains of clams dropped by 

 herring-gulls, which in this instance seemed to have discovered that 

 the road there formed a more suitable surface for the purpose than the 

 nearby shore. 



Gulls like to wash their food, if it is of any size, in water. Herring- 

 gulls may be observed rinsing their fish food in tidal pools. Great 

 black-backed gulls will wash the sea-birds (puffin, shearwater, various 

 auks) and small mammals which they have killed, in the sea, or on 

 the edge of a freshwater pond or stream at their breeding grounds; 

 and they leave behind in these places quite an accumulation of clean- 

 picked skins and vertebrae. 



The beautiful laughing gull [Lams atricilla) , with the dark glittering 

 eye encircled with a fiery ring, is an adept at stealing eggs from the 

 nests of terns ; it also has a trick of alighting on the head of the brown 

 pelican, and snatching food from its pouch. In turn it is much pur- 

 sued by skuas and man-o'-war birds. 



Goethe (1937) has given us one of the best accounts of the breeding of 

 a Lams gull in his study of the herring-gull breeding among sand- 

 dunes. His descriptions of courtship, display and nesting may be 



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