426 THE DESCENT OF MAN. 



rook is known to alter during the breeding-season, and is 

 therefore in some way sexual.* But what shall we say 

 about the harsh screams of, for instance, some kinds of 

 macaws; have these birds as bad taste for musical sounds 

 as they apparently have for color, judging by the inhar- 

 monious contrast of their bright yellow and blue plumage? 

 It is indeed possible that without any advantage being thus 

 gained, the loud voices of many male birds may be the 

 result of the inherited effects of the continued use of their 

 vocal organs when excited by the strong passions of love, 

 jealousy and rage; but to this point we shall recur when we 

 treat of quadrupeds. 



"We have as yet spoken only of the voice, but the males 

 of various birds practice, during their courtship, what may 

 be called instrumental music. Peacocks and birds of 

 paradise rattle their quills together. Turkey-cocks scrape 

 their wings against the ground, and some kinds of grouse 

 thus produce a buzzing sound. Another North American 

 grouse, the Tetrao umbdlus, when with his tail erect, 

 his ruffs displayed " he shows off his finery to the females 

 who lie hid in the neighborhood," jdrums by rapidly striking 

 his wings together above his back, according to Mr. K. 

 Raymond, and not, as Audubon thought, by striking them 

 against his sides. The sound thus produced is compared 

 by some to distant thunder and by others to the quick roll 

 of a drum. The female never drums, "but flies directly 

 to the place where the male is thus engaged." The male 

 of the Kalij-pheasant in the Himalayas, " often makes a sin- 

 gular drumming noise with his wings, not unlike the sound 

 produced by shaking a stiff piece of cloth." On the west 

 coast of Africa the little black-weavers (Ploceus?) congre- 

 gate in a small party on the bushes round a small open space 

 and sing and glide through the air with quivering wings, 

 " which make a rapid whirring sound like a child's rattle." 

 One bird after another thus performs for hours together 

 but only during the courting-season. At this season, and 

 at no other time, the males of certain night-jars (Caprimul- 

 gus) make a strange booming noise with their wings. The 

 various species of woodpeckers strike a sonorous branch 

 with their beaks with so rapid a vibratory -movement that 



*Jenaer, " PliilosopU. Transactions," 1824, p. 20. 





