ALARM-NOTES 25 



common illustration of the general rule that when a 

 vocal sound is employed for the expression of an 

 emotion, and the emotion becomes intensified, the 

 note is uttered more frequently, and at a higher pitch. 

 Of course the blackbird is often alarmed suddenly, 

 and then he utters his full alarm at once ; but when 

 his young are threatened, as it seems to him, by 

 the presence of another animal, the construction of 

 the full alarm-cry is sometimes beautifully demon- 

 strated. If the rapid alarms here mentioned have 

 been originally produced by mere repetition, is it not 

 probable that alarms which invariably consist of a 

 note repeated many times, such as those of the 

 mistle-thrush and the magpie, were evolved in a 

 similar manner? 



Danger-cries were probably often uttered near 

 the nests of many species, as they now are thus 

 employed by the lapwing, blackbird, house-sparrow, 

 chaffinch, willow-warbler, and many others of the 

 same genera ; and they would also have been 

 uttered near the fledged young when these were 

 threatened ; hence the young would have been 

 familiar with these cries, and in due course would 

 have reproduced and perpetuated them. In this 

 way each race would probably have developed its 

 own danger-cry ; for we may be sure that there was 



