A Suggestive Question. 113 



or duties are not strong enough to detain it. The 

 young cuckoos do themselves remain until compara- 

 tively late in the year (September), or until they 

 are strong enough to undertake their flight. What 

 cuckoos of the first year could do, the same birds in 

 their second and subsequent years could surely do 

 also." * 



If the adult cuckoos leave this country because of 

 the failure of food supply — it being said often that 

 they leave this country just when the majority of the 

 summer caterpillars assume the imago stage — the 

 question may well be asked, how do the young birds 

 fare when the larger supply of their natural food is 

 cut off"? Is there a provision in this case for making 

 up for this defect by adapting themselves to other 

 food ; and if they do so, why cannot the adults do the 

 same ? This question is, indeed, a very suggestive 

 one — that the young cuckoo's foster-feeding has pre- 

 pared it for this adaptability, whereas that of the 

 adult has not ; but then there is the further considera- 

 tion and question : why is this adaptability limited 

 only to birds of the year, and why should they in 

 such a matter linger so long behind the old birds ; 

 and, more than all this, why, when they stay in our 

 country so late as end of September and even into 

 October, they should go at all on such a long and 

 perilous journey over lines they have never traced 

 before, when they can adapt themselves to what is 

 properly winter-feeding, and when in various portions 

 of the country there are mild and protected portions, 

 where the cold could not injure them if fair supplies 

 of food were to be had ? 



* Dr. Creighton's Jeitner and Vaccination, p. 14. 



