312 LESSONS FKOM NATUKE. [CHAP. X. 



attracting and stimulating the hens. Thus he admits that 

 &quot; the males will sometimes display their ornaments when not 

 in the presence of the females, as occasionally occurs with 

 the grouse at their balz-places, and as may be noticed with 

 the peacock ; this latter bird, however, evidently wishes for a 

 spectator of some kind, and will show off his finery, as I have 

 often seen, before poultry or even pigs&quot; (vol. ii. p. 86). 

 Again, as to the brilliant Rupicola crocea, Sir E. Schomburgk 

 says : &quot; A male was capering to the apparent delight of several 

 others &quot; (vol. ii. p. 87). 



Mr. Darwin considers singing as well as display of plumage 

 to be one of the attractions for which males are 



Voice. 



selected by females, and that in consequence of this 

 the faculty has been developed in certain species to the degree 

 of perfection which we now find it has attained. There are, 

 however, reasons for thinking that it is by no means the 

 sexual instinct alone which occasions this exercise of the vocal 

 powers. Our author himself admits (vol. ii. p. 52), that at 

 any rate &quot; many naturalists believe that the singing of birds 

 is almost exclusively the effect of rivalry and emulation, 

 and not for the sake of charming their mates ;&quot; and in con 

 firmation of this he mentions an instance of &quot; a sterile hybrid 

 canary bird,&quot; which by its singing demonstrated that the 

 habit is at least &quot; sometimes quite independent of love.&quot; 



It is difficult to suppose that sexual selection can have 

 simultaneously developed in a high degree both power of 

 song and singularity of plumage. Yet the Umbrella bird 

 has both : 



&quot; It has an immense top-knot, formed of bare white quills surmounted 

 by dark-blue plumes, which it can elevate into a dome no less than 

 five inches in diameter, covering the whole head. This bird also has 

 on its neck a long, thin, cylindrical, fleshy appendage, which is thickly 

 clothed with scale-like blue feathers. It probably serves in part as an 

 ornament, but likewise as a resounding apparatus, for Mr. Bates found 

 that it is connected with an unusual development of the trachea and 

 vocal organs. The bird utters a singularly deep, loud, and long-sus 

 tained fluty note.&quot; Vol. ii. p. 58. 



Again, the Bell bird is an instance of the simultaneous 



