BRITISH WARBLERS 



must have innumerable opportunities of hearing the cries, 

 call-notes, and songs of species foreign to this country; yet 

 they fail to incorporate them, to any appreciable extent, with 

 their song. 



The truth is, that much more evidence is required ; it must 

 not be forgotten that my facts are collected from, compara- 

 tively speaking, a very small area. It is possible that the 

 sequence of imitative strains in the song of the male in other 

 parts of the British Islands does not contain the songs of the 

 species mentioned in so large a proportion, but I can scarcely 

 believe that it can be so ; it is more probable that the law of 

 uniformity accompanies the imitative faculty, as it does every 

 other vital manifestation of the animal world, and that for 

 reasons at present unknown to us, certain strains may have 

 been and may be incorporated more readily than others. 



Eeturning once again to the simple explanation with 

 which we set out, namely, individual acquirement, I find it 

 difficult to understand from this point of view why there 

 should be such similarity in the imitations ; for with the 

 imitative faculty so strongly implanted, and with different 

 males living in contact, as they undoubtedly do, with different 

 species, we should here look for and surely expect to find some 

 traces of divergent individualism. 



There is yet another method by which they may have 

 arisen, although, as we shall see, not a very probable one. 

 Many naturalists believe that the type of the song of different 

 species is a matter of tradition, that is to say, that the parents 

 hand it down to their offspring. This hypothesis requires that 

 the young birds should have had predominant opportunities 

 of hearing their parents' song; but the fact seems to have 

 been lost sight of that there are species, and those, too, in 

 which the vocal powers are developed in the highest degree, 

 that are silent during the period in which they are engaged 

 in tending their young, some of them even remaining so until 

 the following spring. The power of imitation must be founded 

 upon a congenital basis, and if the song had been thus handed 



34 



