EVOLUTION OF BIRD-SONG 



the thicket ; the starling to those of the field as 

 well as to those of the town. On further tabulation 

 the notes betrayed indications that summer visitors 

 to this country are imitated more often in spring 

 and summer than in autumn and winter, and this 

 would seem reasonable to any one sufficiently familiar 

 with song-birds to understand that many of them 

 are creatures of intelligence, endowed with accurate 

 memories and considerable powers of observation 

 and mimicry. The various aspects of imitation, 

 and instances of its occurrence, are discussed in the 

 chapter on " The Influence of Imitation," towards 

 the end of this book. In pursuing my studies of 

 the notes of birds, I observed a good deal of bird- 

 life, and soon found that certain cries were employed 

 by birds as call-notes, and others for the purpose 

 of expressing alarm — facts which have long been 

 familiar to ornithologists. I also noticed that birds 

 of a species would generally behave in much the 

 same manner on the same occasions, and that par- 

 ticular cries were sometimes employed to express 

 certain degrees of emotion, some call -notes being 

 evidently of a more urgent meaning than others, 

 and some alarm -cries being similarly more im- 

 portant. There were other curious features in 

 these call-notes and " alarms," which are respectively 



