Cow-Birds Destructive. 247 



respect of immense superiority of males in numbers ; 

 and (2) as regards changed conditions on the country 

 in the way of cultivation influencing these to the 

 formation of certain habits, etc. ? And what about 

 the reason here advanced for large numbers of eggs, 

 and how far does it apply to our cuckoo ? 



VI. The fact that an egg put into a nest of any 

 species alone before the true bird has laid any will 

 almost infallibly cause that nest to be deserted proves 

 that the victimised birds are then sharp enough to 

 recognise an egg not their own, the nest being so 

 invariably deserted. Abundant authority there is to 

 this efl'ect. 



Mr. Nuttall states that if a cow-blackbird's egg 

 is deposited in a nest alone, the nest is uniformly 

 forsaken." 



This fact makes it the more likely that here, as in 

 the case of our common cuckoos, the intruding birds 

 try to remove the true egg or eggs, thus cunningly 

 aiding the duping by preservation of the numbers. 



We read : 



" Probably three-fourths of the lost nests of the 

 scissor-tail (Milvulns tyraniius), are abandoned in 

 consequence of the confusion caused in them by the 

 cow-birds. . . I have seen the female cow-bird strike 

 her beak into an egg and fly away with it ; and 

 watched the male bird, when she quitted it, drop 

 down and begin pecking holes in the eggs." 



In how far are we justified in saying that Canorus 

 does the same ? 



The cow-bird, like certain of our Canorus^ watches 



*P. 157- 



