THE GULLS 247 



much swollen. The bulky mass passes slowly into the crop. An hour 

 or so later it may be thrown up in front of the brother or sister of the 

 murdered chick, which, however, cannot tackle such a gargantuan 

 feast. The adult then usually re-devours the horrid mess. It may 

 be that the cannibal throws up the meal less with a desire to feed its 

 young, than to relieve its crop ; but if so, having relieved its crop, it is 

 immediately hungry again and, after a further battering, the pulpy 

 remains of the chick are swallowed once more. 



This cannibalism is prevalent among the great and lesser black- 

 backed and herring-gulls, less so in the case of the black-headed 

 gulls and the skuas, and apparently never occurs among kittiwakes. 



Glaucous gulls encourage their young in the art of egg-sucking 

 as soon as they are able to wander and explore, or even in the nest. 

 The adult breaks a hole in the egg (generally of some arctic-nesting 

 duck) and the chick leisurely helps itself Later the fledged deserted 

 gulls gather on the flat tracts along the tundra shore and feed on 

 crow-berries {Empetrum nigrum), eating great quantities in default of 

 other food. 



The picture of the sociable Larus gulls during the summer is hardly 

 a pleasing one; they are shown, by human standards, to be disgusting 

 and cannibalistic. The greatest mortality during the year must occur 

 during the breeding season. That the powerful dominant gull lays two 

 or three eggs each year in order to' maintain its numbers, while some 

 weaker species which the gulls prey upon, such as certain auks and 

 petrels, lay only one egg, is the more comprehensible if we regard 

 cannibalism as an effective controlling factor in the population of larger 

 gulleries. 



By comparison with the Larus gulls the kittiwake is as inoffensive 

 in character as it is charming m appearance. It is true that at the 

 nesting site it is noisy and a little quarrelsome, but this behaviour 

 seems childlike and playful by contrast with the savage habits of the 

 larger gulls. Probably the kittiwake has less opportunity to interfere 

 with its neighbours, since each nest is usually isolated from the next, 

 that is to say it is seldom connected by a bridge of rock over which it 

 is possible for trespassers to walk. Contact between neighbouring 

 nests can only be made by flying, and there is very little serious inter- 

 ference by wandering or unattached birds. The kittiwake never preys 

 upon the eggs of its own kind or of that of any other bird; it lives almost 

 exclusively on small fish, crustaceans, plankton and molluscs taken 

 upon or near the surface of the sea. But it often loses a large proportion 



