90 EVOLUTION OF BIRD-SONG 



We know that certain birds inherit their cries. 

 I propose now to call attention to certain sounds 

 which may be called " family cries," because they are 

 common to species which exhibit physical affinities, 

 and have therefore been classified as belonging to the 

 same families or groups of birds. In dealing with 

 this subject, I do not purpose to distinguish notes 

 perpetuated by inheritance from those perpetuated 

 by mimicry. If the young of some song-birds 

 acquire every danger-cry and call -note solely by 

 imitating the voices of their parents, and keep strictly 

 to these models, and the notes are common to all 

 birds of the same species respectively, a similarity 

 between those notes in allied species is just as 

 valuable an indication of a common origin as it 

 would have been if the perpetuation of the notes had 

 resulted from inheritance. For, in some species, 

 filial mimicry of voice seems to be as powerful as 

 inheritance of form and colour ; but this occurs 

 only in singing birds or in their allies. 



In this chapter it will be necessary to mention 

 many specific and other cries, in such a manner as 

 to convey a definite idea of the sounds under con- 

 sideration. I know how difficult of realisation such 

 attempts must be ; yet I hope that by means of 

 descriptions of the occasions, and of the manners of 



