246 SEA-BIRDS 



fully ejected and they quarrel among themselves for the best bits. 

 The first hatched chick, being usually twenty-four hours or so older 

 than the second, may sustain throughout the fledging period a physical 

 dominance due to its ability to secure the lion's share. Where food is 

 plentiful, however, the three chicks may eventually level up in growth 

 and become indistinguishable from each other, but more often than 

 not, one, and sometimes two, of the younger ones, disappear during 

 the fledging period (this occurs in other species, e.g. the black guille- 

 mot) . They have been underfed as a result of the greed of the first 

 chick, and have become progressively weaker and less able to resist 

 the bullying of the first-born. They die, or are eaten by their own kind, 

 even by their parents who later may feed the partly digested carcase 

 to the survivors. 



It is remarkable that in a large colony of gulls the number of chicks 

 successfully fledged is probably, on the average, much less than one 

 young bird to each pair of breeding adults. Where losses have not 

 iDcen suffered as a result of depredations by man and other animals 

 earher in the breeding season, and young chicks have hatched in 

 fair numbers, great losses may occur as a result of adults preying upon 

 the chicks of their neighbours. Probably the amount of cannibalism 

 in any colony will depend on the abundance of normal fish-food. 

 Kirkman found that young black-headed gull chicks which wander 

 from home are sometimes adopted by chickless adults, but more often 

 are killed by adults with chicks of their own. There is strong evidence 

 that once a very young chick wanders from the nest it may not survive; 

 even when it returns home it may be killed and eaten by its own 

 parents. An example of this type of unreasoning cannibalism may 

 occur when a nestling wanders away among burrows or nests of a 

 species which is normally preyed upon by its parents. Moreau (1923) 

 saw a herring-gull go to its own chick, which had strolled away 

 among puffin burrows, and kill it with great ferocity. We have seen 

 herring-gulls and lesser-black-backs attack chicks of their own species 

 which were wandering among the nests of neighbours, and great black- 

 backs killing and devouring new-born and up to half-grown chicks 

 of the two smaller species. Such chicks are ruthlessly grabbed and 

 battered to death. If small, a chick is swallowed whole, if well grown 

 it is beaten until the bones are broken and the body is more or less 

 shapeless; then it is gulped down in one mass, though often with 

 difficulty. As a rule, after a heavy meal of this sort, the gull will rest 

 for a while, looking very uncomfortable, and at first with the neck 



