RELATIONS TO ANIMATE ENVIRONMENT 117 



and slowly eaten alive by animals so far inferior in the 

 scale." 



Strangely enough, the nestlings of the Booby {Sula leucog- 

 aster) and of the Noddies (A nous stolidus and A. melanogenys) 

 which Moseley found on St. Paul's Rocks, defended themselves 

 vigorously and successfully from the similar attacks of this 

 crab (Grapsus strigosus). 



It may here be noted that while many birds appear to 

 suffer the spoliation of their nests and the slaughter of their 

 young by their more rapacious neighbours, if not with indiffer- 

 ence, at least with but a feeble show of resistance, others 

 profiting by experience have adopted measures whereby they 

 may escape these unwelcome attentions. Thus Moseley on 

 his visit to Inaccessible Island found that feral pigs had nearly 

 exterminated a Penguin rookery on the south side of the island, 

 but a few Penguins remained which had saved themselves by 

 building in holes under stones where the pigs could not reach 

 them. 



Similarly, the Barn Owl {Strix flammed) in Texas and 

 in India, and the Short-eared Owl in the Aleutian Islands, 

 breed in fairly deep burrows, though the causes which have led 

 to this appear to be unknown. 



But besides enemies from without, a very heavy infant 

 mortality is inflicted by ravages from within, by the depreda- 

 tions of predatory birds, which contrive to support themselves 

 and their families by preying upon the eggs and nestlings of 

 their more helpless neighbours. 



An instance of this is furnished by the great breeding colonies 

 of Penguins and Cormorants on Dassen Island, off the Cape of 

 Good Hope. Mr. M. J. Nicoll, a naturalist who visited this 

 island in igo6, found in addition to vast hordes of Jackass 

 Penguins {Spheniscus demersus) ; — it was estimated that about 

 nine millions of these birds were breeding here, laying their 

 eggs in holes — an enormous colony of Cormorants, and con- 

 siderable numbers of Sacred Ibises and Gulls. 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 devilish dexterity if for a moment they were 

 left unguarded : later they took the young. The Ibises appear 



