BIRD MUSIC 25 



Call notes. Besides their songs, birds also make 

 sounds known as "call notes," which differ from 

 their songs in about the same way that human lan- 

 guage differs from human songs. These call notes 

 probably serve the purpose of a language by which 

 birds communicate. They are used by all birds, 

 both male and female, and at all times of the year. 

 Some birds have a great variety of call notes, each 

 representing some emotion, such as a hunger call, 

 given by the young birds in the nest; the lost call of 

 a young bird after leaving the nest; the warning call 

 given to the young to show no signs of life in the face 

 of danger; the recognition call, by which individuals 

 of the same species are brought together in flocks, 

 especially during migration; and the rally cry by 

 which other birds are brought to the spot. An ob- 

 server of the crow has recorded twenty-seven dis- 

 tinct calls for this bird. 



