Chap. XIII. Vocal and Instrumental Music. 



379 



into a melodious love song. In tlie case of the modiQed 

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

 are produced, we know that some birds during their courtship 

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



'Fig. 45. Secondary winc-fpathers of Pipra delicinsa (from Mr. SolatPr, in ' Proc. Zool. 

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

 sponding feathers, ij, e, f, from the feraale. 



a and d, fiftli set-ondary wing-feather of Tiialo and female, upper surface. 



h and e, sixth secondary, upper surface, c and/, &eventh 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. Tlie females, of course, would 

 not notice each slight successive alteration in shape, but only 



