82 EVOLUTION OF BIRD- SONG 



spring it spends a great part of the day in the upper 

 regions of the air." 



Many birds give a fluttering or shaking of 

 the wings as a means of address to their mates ; 

 such are the starling, female house-sparrow, green- 

 finch, and very many other birds which authors have 

 noticed in all parts of the world. The young of 

 many, if not of most species flutter their wings 

 when being fed by their parents ; and it is a 

 common thing for vehement singers to flap their 

 wings or, like the redstart, shake the feathers in 

 their tails when singing. The lark and its near 

 ally, the tree- pipit, fly much more during song in 

 early spring, when they are courting, than in June 

 and July, when their young are out of the nest. 



15. Ventriloquism. In regions where the 

 enemies of birds are numerous, individuals having 

 the power to utter call-notes in such a manner that 

 the exact spot whence the sounds proceeded could 

 not be determined by enemies, would probably 

 enjoy a consequent advantage in the battle of life, 

 and would not necessarily be prejudiced by this 

 circumstance when seeking mates, who would be dis- 

 covered as soon as they had alighted in the vicinity 

 of the exclaimers. Certain it is that several good 

 observers of bird-notes have been deceived by the 



