44 EVOLUTION OF BIRD- SONG 



uttered in autumn and winter, more especially in 

 the early morning hours ; but, notwithstanding this 

 fact, the note appears to be less often used than any 

 other where a call-note might be employed. 



The first call-notes of birds were probably mere 

 adaptations of alarm -cries, the use of which was 

 induced by the influence of mutual aid among 

 associated individuals, by which the danger -cries 

 would have been frequently employed. But the 

 necessities of the young, having relation not so 

 much to danger as to hunger, must have early 

 brought about the use of cries for food. These 

 simple cries, from having been effective in result, 

 would also have been used by the young after 

 leaving the nest, and might then have indicated a 

 desire not only for food, but also for the companion- 

 ship of the parents. Under these circumstances 

 such cries would have become call-notes. 



It is probable that the first cries of the young 

 were merely inherited modes of expressing distress, 

 and were not influenced by mimicry ; for we now 

 find that the young of many species, of limited vocal 

 range, utter cries which are wholly unlike those of 

 their parents. This occurs in several rasorial birds, 

 and others. 



The young of birds which rear large broods would 



