6o EVOLUTION OF BIRD- SONG 



like the recording or recovering of voice by the 

 males. In this connection may be mentioned some 

 duets noticed by Mr. Hudson in his Naturalist in 

 La Plata. Describing certain South American tree- 

 creepers, he says, " On meeting, the male and 

 female, standing close together and facing each 

 other, utter their clear ringing concert, one emitting 

 loud single measured notes, while the notes of its 

 fellow are rapid rhythmical triplets ; their voices 

 have a joyous character, and seem to accord, thus 

 producing a kind of harmony" {op. cit. p. 256). 

 In one species these duets are practised by the 

 young while yet in the nest. Mr. Hudson says of 

 the South American tyrant fly-catcher that in a 

 majority of cases their songs are simply joyous 

 excited duets between male and female. The songs 

 of the woodhewers, or Dendrocolaptidce, also are 

 chiefly duets. " In the red oven-bird {Furnarius) 

 the duet consists of triplets uttered by the male, 

 with a strong accent on the first note, while the 

 female keeps even time with single notes. The 

 fi?tale of this performance consists of three or four 

 notes uttered by the second bird alone, in an ascend- 

 ing scale, the last very piercing " {pp. cit.). 



Darwin considered bird -song a charm or a 

 call - note addressed to the female {Descent of 



