82 BIRDS IN TOWN AND VILLAGE 



And among the listeners you will find the sparrow 

 and tits of various species — ^birds which are never 

 victimized by the cuckoo and do not take him for a 

 hawk since they take no notice of him until the calling 

 begins. The reason that the double fluting call 

 of the cuckoo is not mimicked by other birds is 

 because they can't ; because that peculiar sound is 

 not in their register. The bubbling cry is reproduced 

 by both the marsh warbler and the starling. Again, 

 it is my experience that when a nightingale starts 

 singing the small birds near immediately become 

 attentive, often suspending their own songs and some 

 flying to perch near him and listen, just as they 

 listen to the cuckoo. Birds imitate the note or phrase 

 that strikes them most and is easiest to imitate, as 

 when the thrush copies the piping and trilling of 

 the redshank and the easy song of the ring-ouzel 

 which, when incorporated into his own music, 

 harmonizes with it perfectly. But he caimot flute, 

 and so never mimics the blackbird's song, although 

 he can and does, as we have seen, imitate its chuck- 

 ling cry. 



There is another thing to be considered. I believe 

 that the bird, like creatures in other classes, has his 

 receptive periods, his time to learn, and that like 

 some mammals he learns everything he needs to 

 know in his first year or two j and that having 

 acquired his proper song he adds little or nothing 



