MAKSH WARBLEE 



is incorporated with the song, but often a phrase or a number 

 of phrases from a highly specialised song — sometimes even a 

 complete song of simple type — and where phrases are intro- 

 duced those phrases are in their proper sequence. Let anyone 

 attempt to combine and recombine without pausing an equiva- 

 lent number of tunes, and he will find that some effort is 

 required to do so. There is much yet to be learnt about the 

 power of imitation. For how long is a bird able to retain an 

 alien song in its memory, and to what extent does it add to 

 its store as the season advances ? Nothing in the way of a 

 decisive answer can be given to these questions. But the 

 key to the first is to be found in the answer to the 

 second. "When the males first reach their destination do 

 they reproduce as many alien cries as they are accustomed 

 to a few weeks later in the season ? That they do so is 

 scarcely likely; for as the days pass by new notes must be 

 so frequently copied as to become associated with the song, 

 thereby extending the list of imitations. The tendency to 

 reproduce alien phrases must be founded on a congenital 

 basis. Given this tendency, the rest, it may be said, will 

 follow in due course. There is much to be said for this con- 

 tention. We observe the acquirement actually taking place in 

 the case of birds kept in captivity, and we find that such 

 acquirements are so retained as to be subsequently reproduced ; 

 we also observe a similar process at work in Nature, as when 

 the cry of some species is immediately reproduced by the 

 imitator. At one time or another every imitation must have 

 been an act of individual acquirement. Now we start with 

 a congenital basis, of the origin of which we are completely 

 ignorant. The young bird born in June leaves this country 

 a few weeks later without having had an opportunity of 

 exercising its vocal powers, and probably unacquainted with 

 its ancestral song. In the winter months it hears the songs 

 of many foreign species, of some of our own summer migrants, 

 and possibly even of its own species. With the rise of the 

 sexual instinct its vocal powers begin to develop, and 



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