i8o EVOLUTION OF BIRD-SONG 



than songs, both in individuals and in species, would 

 seem to have existed for a much longer period, and 

 to have thus been more liable to the influences of 

 imitation. Had this always been so, we should find 

 in the call-notes some traces of imitation ; and the 

 sounds most likely to have been imitated would 

 have been those incidental to feeding or to obtain- 

 ing food. This idea is partly supported by the 

 behaviour of the common cock, who, when calling 

 hens to corn, shakes it within his bill, and at the 

 same time utters a series of sounds not unlike those 

 produced by the rattling of grain within his bill. 

 I think the idea is supported by the squealing of the 

 young of the predacious butcher-bird, by various 

 sharp tones of berry- or seed-eating finches, and by 

 some of the sounds uttered by other kinds of birds. 

 There is evidence that some of the song -notes of 

 birds have been developed in the way just mentioned 

 to a semblance of sounds with which the birds are 

 familiar. And in approaching this subject we must 

 remember it is in song that birds first betray most 

 clearly and often their inclination towards mimicry. 

 Some observations subsequently mentioned in detail 

 will prove that several species repeat not only their 

 parents' notes, but also those of other birds around 

 them. There is no ground for supposing that this 



