EVOLUTION OF BIRD- SONG 



more or less imitation was apparent. About two 

 years later I began to make extensive records of 

 the imitations sung by wild birds, my method being 

 to identify the singer, and then to write down the 

 date and place of singing, the state of the weather, 

 number of times of singing per minute, and the 

 particular sounds which appeared to be reproduced. 

 Some of the sounds imitated were rendered with 

 wonderful fidelity by the better mimics, such as the 

 sedge - warbler, starling, and thrush ; other birds, 

 with full-toned voices, as the robin, blackbird, and 

 nightingale, appeared to be able to repeat exactly 

 the musical intervals sung by other birds, but to 

 be unable to render the sounds (especially in the 

 case of harsh sounds) with accurate intonation. 

 Again, some of the singers appeared to whistle 

 their own songs, and then to supplement these 

 with the addition of sounds borrowed from the 

 cries of other birds. 



The blackbird and missel-thrush exemplify this 

 method. But the blackcap, whose voice is as full- 

 toned as that of either of these two, adopted an 

 opposite mode, and commenced its songs with soft 

 imitations of other birds, to conclude them with its 

 own full whistles. I attempted to draw no deduc- 

 tions from my first observations, knowing that 



