430 



THE DESCENT OF MAN, 



The diversity of the sounds, both vocal and instmmental, 

 made by the males of many birds during the breeding- 



Fig. 45. Secondary winjr-feathers of Pipra deliciosa (from Mr. Sclater, in "Proo. 

 Zool. Soc," 18(i6. The three upper feathers, a, b, c, from the male; the three 

 lower correspondinj? feathers, d, e,f, from the female. 



a and d, fifth secondary wing-feather of male and female, upper surface. 



b and e, sixth secondary, upper surface. 



c and/, seventh seconaary, upper surface. 



season, and the diversity of the means for producing such 

 sounds, are highly remarkable. We thus gain a high idea 

 of their importance for sexual purposes, and are reminded 

 of the conclusion arrived at as to insects. It is not difficult 

 to imagine the steps by which the notes of a bird, primarily 

 used as a mere call or for some other purpose, might have 



