BIRDS 1585 



the melancholy voice of the sea-mew, the gabble of 

 ducks, the crowing of the cock, the soft cooing of the 

 dove, the hoarse voice of the corncrake, the ecstatic 

 melody of the bobolink, the cheerful notes of the 

 blackbird, the educated music of the canary, are 

 again a random selection of instances from an al- 

 most infinite medley. It is among the so-called 

 perchers, songsters, or Insessores that we find song 

 really developed, and that for most part in the males, 

 and in highest degree at breeding time. Though the 

 notes are not musically pure, many songs of birds have 

 been expressed in musical notation, and every one is 

 familiar with imitations in word form. Singing is 

 an unbidden expression of emotional energy. It is 

 most marked at the high tide of sexual emotion dur- 

 ing the breeding season. It is best, sometimes solely, 

 developed in the males, who use their powers to at- 

 tract the females, and often vie with one another in 

 so doing. In other cases the note is obviously used 

 as language, expressing alarm and the like, for that 

 some birds are able by voice to convey impressions to 

 one another is indubitable. In so far as the song 

 is an instrument and expression of sexual attraction, 

 it fails to be included among those powers which 

 have been strengthened and developed by sexual 

 selection. 



After the strain of the reproductive period, or 

 sometimes at the low ebb of mid-winter, the old 

 feathers drop off, and birds undergo annual moult. 

 The use of this in replacing breakage, and in fur- 

 nishing a complete machinery for the flight of migra- 

 tion, is very evident; the cause is not yet sufficiently 



