YOUNG BIRDS IN THE NURSERY 83 



proportion to the size of the colony. In the first place, 

 when helpless nestlings are being reared under these 

 conditions rapacious birds and beasts of all kinds are 

 attracted to the neighbourhood, finding an abundance 

 of food at small trouble in the matter of capture. The 

 great breeding colonies of jackass penguins and cor- 

 morants on Dassen Island afford a case in point. 



Mr. J. M. NicoU, a keen ornithologist of wide experience, 

 visited the island in 1906, and found a " rookery " of 

 jackass penguins {Spheniscus demersus) estimated at nine 

 million birds — which, be it noted, all nested in holes — 

 an enormous horde of cormorants, and thousands of 

 gulls and sacred ibises. The gulls and ibises seem to 

 subsist, during the breeding season, on the eggs and 

 young of the cormorants. The gulls displayed a most 

 extraordinary watchfulness over the sitting cormorants, 

 seizing the eggs with a deviUsh dexterity if, for a moment, 

 they were left unguarded : later they took the young. 

 The ibises appeared to content themselves with preying 

 on the young only, which they seized for the sustenance 

 of their own offspring, feeding them on the entrails of 

 their victims. The penguins escaped, owing to their 

 choice of underground nurseries. Not so, however, the 

 Adelie penguin of the Antarctic, which nests in the open, 

 and whose inveterate enemy is McCormick's skua. 



Dr. E. A. Wilson, one of the naturalists to the Discovery 

 expedition, tells some lurid stories of this gull. " Hanging 

 round the rookery," he says, " with the unmistakable look 

 of a thief, the skua will run up to a chicken almost as 

 big as himself, drag it by degrees away from the more 

 crowded parts of the rookery, and then gradually worry 

 it to death. . . . The penguin chick pipes his loudest, 

 but the old birds standing round take very little notice. 



