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. W^hat 

 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 Jenncr and Vaccination, p. 14. 



