VARIA TION IN BIRD- VOICES 145 



the same, but each certain melodies of its own." 

 Bechstein noticed differences in the songs of nightin- 

 gales, as, indeed, would any close observer. He 

 remarks : " For among these, as among other musi- 

 cians, there are some great performers and many 

 middling ones" (pp. cit. p. 214); and quotes Daines 

 Barrington for the statement that some are so 

 very inferior as not to be worth keeping by the 

 bird-catchers (pp. cit. p. 219). A hundred years ago 

 White of Selborne saw wood -warblers shivering 

 with their wings a little, as they do now, when they 

 made their sibilous, grasshopper- like noise in the 

 tops of high beech-trees (Nat. Hist. Selborne, p. 36). 

 It is evident from the number of instances of varia- 

 tion recorded by ornithologists that it occurs in the 

 voices of all birds ; nevertheless, the prevalence of 

 characteristic phrases, betraying but slight trace of 

 deviation in individuals, indicates that the tendency 

 to vary is perpetually counteracted by others which 

 conserve old characters in song. It appears that 

 the emulation and vehemence of the males are the 

 chief factors in the originating of variations, and 

 that their emotions may in this respect chiefly be 

 counteracted by the selection of female birds ; for 

 these, possessing limited voices, seem to have pre- 

 ferred males whose notes did not greatly differ from 



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