Common Cuckoo. 287 



conventionally) assigned by common consent to the Cuckoo's egg, 

 and the exceptions (also allowed to be numerous) when the egg 

 of that bird resembles those of the species in whose nest it is laid. 



On these two points most of those who have examined the 

 question are, I think, agreed; but beyond this opinions differ 

 widely ; and when we come to discuss the probable reasons for 

 such variation in colour, and assimilation of colour to the eggs 

 of the selected foster parents, there are almost as many theories 

 as disputants, but none of these appear to my judgment so con- 

 vincing, or indeed so plausible, as the original motive assigned 

 by Dr. Baldamus and his followers. 



And then I ventured to put forth a notion which had occurred 

 to my mind, and which has since become with me a fixed opinion, 

 that the young Cuckoo derives from its foster-parent so much of 

 that nurse's nature (whether by the diet on which it has been 

 brought up, on which exclusively the young of the foster-parent 

 would, had it survived, have been fed, or otherwise) as, when its 

 own turn for breeding arrived, to affect (though unconsciously to 

 itself) the colouring of the eggs it laid. In support of that 

 opinion, I would submit the following considerations. 



First I would mention as worthy of observation that the young 

 Cuckoo has been oftentimes declared to have acquired the exact 

 'note of its foster-parents. Of this Mr. Thompson gives decisive 

 evidence in the case of a young Cuckoo which was taken out of 

 a Titlark's nest, and of which he says/ for several weeks after the 

 Cuckoo was placed in confinement it uttered, when in want of 

 food, a note so closely resembling that of the Titlark that it would 

 have been almost impossible to distinguish between them.'* It is 

 true this may be mere mimicry, or the result of imitation ; 

 but it must be remembered that, in calling for food, the young 

 Cuckoo can only imitate the note of its foster-parents, its foster- 

 brethren having perished on its account in their infancy. 

 Here then we have the young Cuckoo in one important respect 

 partaking of the nature of its foster-parents. I do not, however, 

 wish to push this point too far, or to lay greater stress upon it 

 * ' Natural History of Ireland,' vol. i., p. 360. 



