Natural History 437 



the foot of the windpipe in a special enlargement called the song- 

 box or syrinx. The sounds are due to the rapid passage of the 

 air over the tense cords. In the course of evolution the signifi- 

 cance of the voice has broadened out. From a simple parental 

 call it became a means of recognition of any kindred, and in the 

 course of ages it became expressive of particular emotions- 

 emotions of joy and of fear, of jealousy and of content. While 

 a certain amount of vocal ability is part of the hereditary make- 

 up, there seems little doubt that the gift requires educating. The 

 song of the first year is sometimes what one might call tentative 

 and generalised. It improves with practice and is probably 

 helped by emulation and imitation. The way in which some 

 birds, e.g., skylarks, steal snatches of one another's music, suggests 

 the importance of imitation as a factor in educating the vocal 

 powers. 



Song 



We have spoken of song as the vocal part in the display of 

 courtship, but it would be wrong to think of it as being no 

 more. Song is, indeed, not confined to the breeding season, but 

 the periods differ with the species ; the extent to which the females 

 can sing also varies. It is not possible to draw a sharp dividing 

 line between true song and the notes which constitute the ordinary 

 language of birds, and this gives another reason for not over- 

 emphasising the sexual significance of song. 



The definition of song must not be too strictly confined to 

 notes which sound musical to human ears. Outside the ordinary 

 song-bird group, there is quite commonly found some note or cry 

 which is especially associated with the breeding season and which 

 may be regarded as the equivalent of a song. Many of these 

 cries seem harsh and discordant to us, but others have an obvious 

 charm, at any rate, in their native surroundings ; amid the rugged 

 beauty of a wild moorland the weird bubbling spring-call of the 

 Curlew is perhaps more appropriate music than the dainty lilt of 



