52 EVOLUTION OF BIRD- SONG 



call-note a whistle sounding like the word tewy, 

 and slurred upwards in this manner 



8ve. 



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but rendered at a higher pitch. With progressive 

 variations he sometimes constructs from this cry his 

 beautiful song, which can hardly be reproduced in 

 notation, but may be suggested thus : 



The above note tewy is a call - note of the 

 nightingale to its young, and is uttered by this 

 bird at the commencement of about one-fourth of 

 its phrases. I have often heard it repeated longer, 

 and gradually more drawn-out, until the well-known 

 long notes of the nightingale were produced in their 

 typical character. 



Then, also, the nuthatch repeats his full-toned 

 cry tewit, which at all seasons we hear about the 

 elms, so quickly that he produces a full, prolonged, 

 bubbling cry, in character resembling the rolling 

 " water-bubble J: notes produced by a quill whistle 

 blown in water. The skylark, whose first efforts 

 towards song may be heard in autumn and 



