u6 ROUND THE YEAR 



the Cuckoo's egg in the nest of a Green-Linnet, which 

 begins very early to feed its young with vegetable 

 food, I was apprehensive till I saw this fact that this 

 Bird would have been an unfit foster-parent for the 

 young Cuckoo. 



" There seems to be no precise time fixed for 

 the departure of young Cuckoos. I believe they go 

 off in succession, probably as soon as they are capable 

 of taking care of themselves. Though they stay here 

 till they are nearly equal in size and growth of 

 plumage to the old Cuckoo, yet the fostering care of 

 the Hedge-sparrow is not withdrawn from them. I 

 have frequently seen the young Cuckoo of such a size 

 that the Hedge-sparrow has perched on its back or 

 half-expanded wing, in order to put the food into its 

 mouth. At this advanced stage, I believe that young 

 Cuckoos procure some food for themselves. If they 

 did not go off in succession, it is probable that we 

 should see them in large numbers by the middle of 

 August, but they are not more numerous at any 

 season than the parent-birds in May and June." 



The habits of the Cuckoo afford a tempting field 

 for speculation, and many attempts have been made 

 to trace the probable origin of the instinct which 

 leads this Bird to lay her eggs in the nests of others. 

 Jenner, as we have seen, looks upon the necessity of 

 early migration from the north as the determining 

 cause. But the early migration is still an unexplained 

 fact. Is it an antecedent or a consequent? "Does 

 the Cuckoo lay her eggs in other Birds' nests, in 

 order that she may leave early, or does she leave 



