i86 E VOL UTION OF BIRD-SONG 



some boisterous, or musical little cataract, whose 

 persistent notes may fairly be expected to influence 

 the future songs of nestlings reared in the neighbour- 

 ing shade. For, in view of the influences which 

 may affect their song in a cage, can we come to any 

 conclusion other than that they would be affected 

 by, and would tend to reproduce distinct musical 

 murmurs of a brooklet close at hand ? The song of 

 the British Columbian wren, before mentioned, seems 

 to prove, almost incontestably, that such an original 

 has been imitated by that bird. 



Resemblances to Sounds produced by 

 Insects 



The sounds made by insects are infinitely less 

 persistent than the sounds made by streams, and 

 hence they would be less likely to influence the 

 notes of imitative birds. Wilson stated that the 

 American field -sparrow {F. pus ilia) has "no song, 

 but a kind of chirruping not much different from 

 the chirruping of a cricket." The bird seems to be 

 partial to thickets {op. cit. vol. i. p. 266). Gilbert 

 White observed that the jar of the nightjar re- 

 sembled the jar of the mole cricket (Miscell. Observ. 

 in Jesse's Gleanings^ p. 286). The song of the grass- 

 hopper-warbler is exactly like the persistent song of 



