Chap. XI II. Vocal and Instrumental Music. 



379 



into a melodious love song. In the case of the modified 

 feathers, by which the drumming, whistling, or roaring noises 

 are produced, we know that some birds during their courtship 

 Cutter, shake, or rattle their unmodified feathers together ; and 



a 



d e 



Fig. 45. Secondary wing-feathers of Pipra deliciosa (from Mr. Sclater, in ' Proc. Zool. 

 Soc.' 1860). The three upper feathers, a, b, c, from the male; the three lower corre- 

 sponding feathers, d, e,f, from the female. 



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



b and e, sixth secondary, upper surface, c and/, seventh secondary, lower surface. 



if the females were led to select the best performers, the males 

 which possessed the strongest or thickest, or most attenuated 

 feathers, situated on any part of the body, would be the 

 most successful ; and thus by slow degrees the feathers might be 

 modified to almost any extent. The females, of course, would 

 not notice each slight successive alteration in shape, but only 



