THE CUCKOOS AND THE OUTWITTED COW-BIRD 43 



tice, though such acts are apparently accidental 

 rather than deliberate, so far as parasitical intent 

 is concerned. The lapse is especially noticeable 

 among such birds as build in hollow trees and 

 boxes, as the woodpeckers and wagtails. Thus 

 the English starling will occasionally impose 

 upon and dispossess the green woodpecker. In 

 the process of nature in such cases the stronger 

 of the two birds would retain the nest, and thus 

 assume the duties of foster-parent. Starting from 

 this reasonable premise concerning the prehis- 

 toric cuckoo, it is not difficult to see how natural 

 selection, working through ages of evolution by 

 heredity, might have developed the habitual resig- 

 nation of the evicted bird, perhaps to the ultimate 

 entire abandonment of the function of incubation. 

 Inasmuch as " we have no experience in the crea- 

 tion of worlds," we can only presume. 



Indeed, the similarities and contrasts afforded 

 by a comparison of the habits of all these birds — 

 European cuckoo, American cuckoo, and cow-bird 

 — afford an interesting theme for the student of 

 evolution. What is to be the ultimate outcome 

 of it all? for the murderous cuckoo must be con- 

 sidered merely as an innocent factor in the great 

 scheme of Nature's equilibrium, in which the de- 

 vourer and the parasite would seem to play the 



