i66 A HISTORY OF BIRDS 



procuring mates is shown in the case of the British Warblers, 

 where the males arrive before the females, and take up their posi- 

 tion for the summer. This done, the females on their arrival are 

 attracted to the chosen sites by the sound of the familiar song, 

 probably electing to alight within the area of the troubadour 

 which pleases most. 



That the song of any given species varies with the geo- 

 graphical range of that species has often been denied ; but never- 

 theless it would seem to be true. 



Although it is commonly supposed that true .song-birds sing 

 only when extremely happy, only when possessed by some spasm 

 of exaltation, so to speak, this is by no means altogether the 

 case. The most famous singer of all, for example, the Night- 

 ingale, will sing when alarmed, or under the emotion of a great 

 shock, as when its nest and eggs are destroyed, or when roused 

 from sleep by some sudden alarm. 



V. Instrumental Mu.sic 



Though by no means generally known, it is nevertheless a 

 fact that many birds possess the power of making sounds by 

 mechanical means : sounds which may not be musical to cultiv- 

 ated ears, but which are nevertheless at least as worthy of this 

 designation as the music of savage peoples. 



We can distinguish wind-instruments and instruments of 

 percussion. And while in some cases the males alone play, in 

 others both sexes appear to be equally skilled performers. 



Among wind-instruments one of the most remarkable is that 

 of the Emu. In both sexes of this bird the outer wall of the 

 windpipe is pierced near the middle of its length for a space of 

 several inches ; and through this aperture the inner lining of the 

 windpipe escapes to form a large inflatable sac lying immedi- 

 ately under the skin. Therewith these birds make a very re- 

 markable sound which resembles the " rolling " of a big drum. 

 But whether this noise is made only during the courting season, 

 as a kind of music, or whether it is used as a call-note at all 

 seasons, does not appear to be known. 



In many species of Cranes and Swans the windpipe has 

 undergone a no less remarkable modification. Herein it has 

 greatly increased in length, the additional inches being stowed 

 away in a long chamber formed by the keel of the breast-bone, 



