150 Summer Studies of Birds and Books chap. 



bird, they •will acquire that bird's song, and if with 

 birds of two or three different species, their song will 

 probably be a mixture. But when once a lesson is 

 thoroughly learnt, it seems to be rarely forgotten : 

 they will not desert one song and take up another, 

 however often they may hear it. 



These experiments of Barrington's, and some 

 others also, do undoubtedly prove that even if birds 

 have an hereditary tendency to sing the song of their 

 own species, it may be easily overcome, and bent in 

 another direction, by placing them within hearing of 

 the songs of other birds. But I cannot help thinking 

 that the subject needs more careful investigation, and 

 that there are difficulties which are not yet cleared 

 up. For example, how does the young Cuckoo learn 

 the note of his own species ? He is brought up in 

 an alien nest, and hears the song and the alarm-notes 

 of his foster-parents. Some say that the parent 

 Cuckoo continues to feed the young bird, and haunts 

 the nest for some time, though that has not been the 

 case within my own experience. If that be so, it 

 might be argued that the young Cuckoo, whose voice 

 organ is not, I suppose, suited to produce the notes 

 of a Tree-pipit or Wagtail or Dunnock, naturally 

 imitates the voice of its true parent. But there is 

 again a difficulty : by the time the young bird is 

 hatched, the old Cuckoos are rarely heard, and have 

 in any case lost the true intonation of their song. 



