THE LOVE DISPLAYS OF BIRDS 215 



endless ways. Another almost equally remark- 

 able feature about avine song is what we may 

 term the capriciousness of its possession. Few 

 species form their songs out of the same com- 

 bination of notes, and in many instances very 

 closely allied birds differ remarkably in the 

 quality of their voice. As a familiar instance 

 we have the Willow Wren and the ChiffchafT, 

 both very common little spring visitors to Eng- 

 land, and so much alike that it requires some 

 considerable knowledge of birds to distinguish 

 them. But the Willow Wren possesses a charm- 

 ing and plaintive song, a little run of beautiful 

 notes that form one of the sweetest bird-sounds 

 in spring, whilst the Chiffchaff's attempt at 

 music only amounts to a monotonous double 

 note, not easily mistaken for that of any other 

 British species. The high degree of organisa- 

 tion of the Passeriformes, and the fact that the 

 special vocal organs for producing true song 

 are peculiar to them, seem to indicate that the 

 group is comparatively a recent one. The 

 logical inference from this is that Song is but 

 a recent acquirement among birds, and that the 

 earth during the earlier eras of avine evolution 

 was absolutely wanting in avine melody. 



Much diversity of opinion prevails concerning 



