6 Life History of Common Cuckoo. 



owing wholly to the conditions in which I kept my 

 canaries and finches — free at certain times to fly 

 about the room, in one end of which I had my aviary. 



This tendency of seed-eating birds to vary from 

 seed-eating, more especially at the time of feeding 

 young ones, would thus be all in favour of the young 

 cuckoos. If they rejected the seed diet, they would 

 come in for relief through the insects, for which the 

 foster parents would now be on the look-out ; and a 

 question may well here arise whether these facts may 

 not have had their own influence in turning certain 

 seed-eaters more and more definitely into insect-eaters 

 during the period of feeding the young. 



On the other hand, there are several birds, among 

 them the Blackcap and the Garden -warbler, which, 

 though set down in bird-books as insect-eaters, are 

 largely seed and berry-eaters too, and there can be no 

 doubt that blackcaps often remain in this country all 

 the winter, managing to " make a do of it," as London 

 working women say, by aid of elderberries, mountain- 

 ash berries, and other berries. 



The crossbills are put down in some ornithological 

 handbooks as feeding entirely on fir seeds, but they 

 feed freely on aphides, small flies, and minute beetles, 

 and this more especially at the period of rearing the 

 young.''- 



Even linnets will turn insect-eaters at breeding 

 and other times. We read : 



" In 1 891 there was a plague of black diamond 

 moth caterpillars. Rooks, plovers, seagulls, starlings, 

 linnets, greenfincheSy and yellowhammers all turned 

 to police duty and ate the grubs. Only the sparrows 



* Zoologist, 1895, P- 228. 



