12 OUR FAVOURITE SONG BIRDS 



notes, and it is a fact which every observer will 

 soon recognize, that very closely allied birds differ 

 to an astonishing degree in the quality of their 

 voice. We could not have a better example of 

 this than that furnished by the Willow Wren and 

 the Chiffchaff. These two birds are so much alike 

 that it requires a person with some considerable 

 knowledge to distinguish them, yet the songs of 

 the two species are so utterly dissimilar that no 

 one could possibly confuse one with the other. 

 The Willow Wren's song is sweet and plaintive, 

 a little run of beautiful notes ; whilst that of the 

 Chiffchaff is a monotonous double cry, not easily 

 mistaken for that of any other British species. If 

 we admit that song is a secondary sexual character 

 this diversity need not surprise us, for of all characters 

 this is the most variable We may here remark that 

 only in the Passeres do we find birds of true song — 

 birds which are distinguished from all others by the 

 organs at the end of the windpipe being specially 

 developed for the production of these sweet sounds, 

 the sweetest by far in all animated nature. This 

 organ of voice, technically called the "syrinx," is 

 really a modification of the lower part of the trachea, 

 and consists of a series of muscles attached to the 

 extremities of the bronchial semi-rings. 



There has been much diversity of opinion 

 expressed concerning the origin and purpose of 

 Song. It is a popularly prevailing idea that song, 



