86 BIEDS 



eggs to those of its mother, and itself also deposit them 

 in wagtails' nests, I am unable to say, but I think it 

 probable that such is the case. I presume that the 

 various types of cuckoo's eggs have all been gradually 

 evolved from a common stock, and this could hardly have 

 happened if the young birds did not follow the rule of 

 their parents. It must, however, be admitted that, in 

 order to accept this view, one is almost compelled to 

 assume that the paternity of a female bird has no influence 

 on the colour of its eggs, but this does not seem to me 

 to present an insuperable difficulty. 



There are several other species of birds which, for no 

 apparent reason, lay two or more entirely different types 

 of eggs. Ked-backed shrikes, blackcaps, garden warblers, 

 and tree pipits occur to me at once, and I have no doubt 

 that there are several others. 



In the case of the first-named bird I have been told I 

 believe by Mr. Hart that in its first year it lays the red 

 eggs, and in its second and succeeding years the greenish 

 brown ones, but this theory can hardly be extended to 

 the blackcap, which lays three distinct types of eggs. The 

 only explanation of this difficulty that I can offer is that 

 there were originally three distinct species of bird of the 

 warbler tribe, and that they have now become merged 

 in the blackcap. 



A. W. T. 



IV 



With reference to your interesting article on the cuckoo, 

 published in the Spectator of April 21, the writer of the 

 article seems to suggest that the cuckoo has the power of 

 imitating the colouring of the eggs of the future foster- 

 parents. Is it not much more probable that the cuckoo 

 after laying the egg, selects the nest which contains eggs 

 most nearly resembling its own? I have more than once 

 found the egg of a cuckoo, perfect, and placed carefully 



