88 SPRING 



fulness of the cuckoo's parasitism if we could be sure that 

 these rude platforms represented a struggle towards a decent 

 family life on the part of former polyandrists and infanticides. 

 But it may be just the other way round. These American 

 cuckoos may be losing the habit of building nests, and the 

 next stage may be to put their eggs in the nests of other 

 birds, as our cuckoo does. Starlings sometimes lay an egg 

 among those of jackdaws ; and pheasants will also lay in 

 other pheasants' nests. But we have never heard of a 

 young starling being hatched and brought up among a 

 brood of jackdaws, and the strangest acquisition of all is 

 the young cuckoo's innate impulse to throw out its foster- 

 brothers. 



Undetained by family cares, old cuckoos migrate early in 

 August, when the hairy caterpillars on which they live are 

 getting scarcer. The young remain a month or six weeks 

 later ; and in their case, at any rate, there can be no question 

 of the migratory habit being due to the example of their 

 parents. Though in late August and September there is no 

 such profusion of hairy caterpillars as in the copses of June, 

 the large caterpillars of the buff-tip moth are in the boughs 

 until September is far gone. Earlier in their history the 

 young cuckoos live on more diversified fare. They are 

 naturally fed on the food which their foster-parents give their 

 own young, and since they are brought to the light in the 

 nests of seed-eating as well as insect-eating birds, it might be 

 thought that in such cases they would be given very unsuit- 

 able food. This is avoided by the provision of nature, which 

 arranges that even the seed-eating birds are fed in the 

 earliest weeks of their life on caterpillars and other insect food. 

 The diet proper to a young chaffinch thus suits the young 

 cuckoo as well as that of a young hedge-sparrow ; the only 

 difference is that he requires four or five times as much. For 



