56 Life History of Common Cuckoo. 



*' It is supposed that the colouration of the cuckoo's 

 egg is an hereditary faculty, and that each female 

 cuckoo lays a particular type of egg. This is in all 

 probability the case, and cuckoos which lay blue eggs 

 come of a stock which has been hatched from blue 

 eggs, and will continue to lay them and deposit tJiejii 

 in the nest of some hlue-egg-laying species.'''''' 



Set this against the following: "In none of the 

 hedge-sparrows' nests, for instance, have we a blue 

 cuckoo's egg.'' Another authority puts it that canorus 

 *' will by preference lay in the nest of the species 

 which brought her up." The great comparative 

 number of blue cuckoos' eggs laid in the nests of 

 birds with brown-blotched and even lark-like eggs, 

 and, more still, eggs like those of the nightingale, 

 suffices to prove that there must be so very many ex- 

 ceptions to the rule laid down in the words italicised 

 above that it is completely invalidated, and so far as 

 that point is concerned cannot be said to give force 

 to the reason for the production of blue eggs in certain 

 families of the cuckoo. It is a very good theoretic 

 reason to justify, as it were, a hard and fast theory of 

 radical differentiation of cuckoos into blue egg-laying 

 and other egg-laying faniiUes ; but facts are against it 

 clearly enough ; seeing that in so many instances the 

 blue eggs are not laid in the nest of some blue egg- 

 laying species — and thence a mere waste of more 

 specialised colouration — since, surely, it would have 

 been a gain to have better matched the eggs, were it 

 only that bird-nesters and even ornithologists might 

 have been more completely and longer deceived ; 

 though it is difficult to see how if, in times past, blue 



* Allen's Handbook, ii, p. 28 



