An Easy Assumption. 139 



Mr. H. S. Rodney reports having found in Pots- 

 dam, N.Y., May 15th, 1868, a nest of Zonotrichia 

 leucophrys (white-crowned sparrow), of two stories, in 

 one of which was buried a cow-bird's egg, and in 

 the upper there were two more of the same, with 

 three eggs of the rightful owners. 



Mr. E. A. Samuels, in 1862, wrote: " Some birds 

 build over the strange egg a new nest." * 



Mr. Romanes writes : 



" We may perhaps at first sight wonder why some 

 counteracting instinct should not have been developed 

 by the same agency in the birds which are liable to 

 be thus duped ; but here we must remember that the 

 deposition of a parasitic egg is, comparatively speak- 

 ing, an exceedingly rare event, and therefore not one 

 that is likely to lead to the development of a special 

 instinct to meet it." 



See how nicely here the whole difficulty is got rid 

 of by an easy assumption ! But there are instances of 

 birds — wrens, reed-warblers, robins, wagtails, etc. — 

 abandoning nests because of the intrusion of a cuckoo's 

 egg. I myself have met with two cases in North- 

 East Essex, wherein certain parts cuckoos so abound, 

 that I do not agree with Mr. Romanes that the de- 

 position of a cuckoo's egg there is "an exceedingly 

 rare event." The nest of a wood-pigeon, and the nest 

 of a sedge-warbler, and, in a third case, in the nest 

 of a reed-wren, the cuckoo's egg was thickly rolled 

 in small leaves and moss at the bottom, and put to 

 one side, that it might not be hatched by receiving 

 heat from the sitting bird's body. Now, here the 

 question for Mr. Romanes's disciples, admirers, and 



* Birds of New England, p. 340. 



