CHAPTER V 



THE SIMPLEST SONGS 



AT the commencement of the breeding season birds 

 of opposite sex call to each other ; and this vocal 

 exercise is especially performed by the males. I 

 know of no species (except, perhaps, the mute 

 swan) in which this behaviour does not occur. As 

 the increase of fear induces amongst birds in com- 

 pany a more frequent repetition of an alarm-cry, 

 so love stimulates the male to a more rapid re- 

 petition of his call-notes. In some species there 

 is apparently a diversity of call-notes ; but it will 

 be observed that generally a particular cry is 

 employed by both sexes. At the commence- 

 ment of this season, then, the kestrel repeats his 

 cry to his mate ; the rook calls loudly and in- 

 cessantly from the selected site for the nest ; the 

 tree-creeper repeats with unusual rapidity his long- 

 drawn and plaintive note ; the wryneck cries con- 

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