CONCERNING THE CUCKOO 115 



to the development of the bird along such a peculiar 

 line? 



The proper point at which to begin an inquiry 

 of this nature would seem to be that to which all 

 the theorists are willing to return. There can be 

 no doubt that the cuckoo, like all parasites, at one 

 time lived a respectable existence. The bird must 

 at some time or other have built a nest and reared 

 its own young. There are many recorded observa- 

 tions of the reversion of the bird at the present day 

 to this long lost and aboriginal instinct of nidification. 

 The cuckoo has been seen to sit on her own eggs 

 on the ground, and she has been observed feeding 

 her own young. It is even stated that she sometimes 

 makes attempts at nest-building. Herr Adolph 

 Miiller has recently given an account of a case 

 which he claims to have observed of a cuckoo hatch- 

 ing her own eggs. Comparing the cuckoo at the 

 present day with other birds nesting under normal 

 conditions, we find the parasitic habit associated 

 with three remarkable characteristics. There are : 

 (i) the undoubted gluttony of the bird and the 

 peculiarity of its food ; (2) the great preponderance 

 of males ; and (3) the extraordinary habit of the 

 young cuckoo in the nest. Any theory of the origin 

 of the cuckoo's habits through natural selection 

 should be able not only to account for the parasitic 

 instinct, but to explain in what way these peculiari- 

 ties are associated with this instinct and with each 

 other. 



The only other bird in which the cuckoo's habits 

 are known to be developed to a considerable extent 

 is the American cow-bird. These birds exhibit in 

 different degrees habits with regard to their eggs, 



