1 62 E VOL UTION OF BIRD- SONG 



during the preceding half-hour. Fish, again, and 

 some insects also, are particularly liable to follow 

 each other ; and here imitation may influence the 

 choice of direction. 



In treating of the influence of heredity, I have 

 shown that the young of several species of birds 

 inherit their cries ; and indeed it is probable that, 

 speaking generally, the cries of birds which have 

 limited voices are inherited, and that those of what 

 are commonly called " singing-birds " are perpetuated 

 through the agency of mimicry. Certain it is that 

 the call-notes of the fowl, pheasant, turkey, partridge, 

 duck, goose, and common shelduck are inherited ; 

 those of the pigeon, cuckoo, crow and his allies, 

 hawks and their allies, sea-birds, and others of 

 limited voices, are probably inherited, but may be 

 transmitted by imitation ; while the cries of some of 

 the finches and warblers are certainly perpetuated 

 through the latter agency, and the songs of a large 

 number of these last certainly are greatly affected 

 by its influence. The effects of this influence are 

 wide-spread amongst captive song-birds. Who has 

 not heard a caged finch, or lark, blackbird, thrush, 

 or starling which was said to have " caught," as it 

 reproduced in its song, the notes of one or more 

 neighbouring birds ? Such instances are very 



