220 SEXUAL SELECTION: BIRDS. [Pakt IL 



ment as taste, we can understand how it is that within the 

 same group of birds, with habits of life nearly the same, 

 there should exist white or nearly white, as well as black, 

 or nearly black species — for instance, white and black 

 cockatoos, storks, ibises, swans, terns, and petrels. Pie- 

 bald birds likewise sometimes occur in the same groups, 

 for instance, the black-necked swan, certain terns, and the 

 common magpie. That a strong contrast in color is agree- 

 able to birds, we may conclude, by looking through any 

 large collection of specimens or series of colored plates, 

 for the sexes frequently differ from each other in the male 

 having the pale parts of a purer white, and the variously- 

 colored dark parts of still darker tints than in the female. 



It would even appear that mere novelty, or change for 

 the sake of change, has sometimes acted like a charm on 

 female birds, in the same manner as changes of fashion 

 with us. The Duke of Argyll says ^^ — and I am glad to 

 have the unusual satisfaction of following for even a short 

 distance in his footsteps — "I am more and more convinced 

 that variety, mere variety, must be admitted to be an ob- 

 ject and an aim in Nature." I wish the Duke had ex- 

 plained what he here means by Nature. Is it meant that 

 the Creator of the universe ordained diversified results for 

 His own satisfaction, or for that of man? The former no- 

 tion seems to me as much wanting in due reverence as the 

 latter in probability. Capriciousness of taste in the birds 

 themselves appears a more fitting explanation. For ex- 

 ample : the males of some parrots can hardly be said to 

 be more beautiful, at least according to our taste, than the 

 females, but they differ from them in such points as the 

 male having a rose-colored collar instead of, as in the fe- 

 male, "a bright emeraldine narrow green collar;" or in 

 the male having a black collar instead of " a yellow dcnii- 

 collar in front," with a pale roseate instead of a plum-blue 



'« 'The Journal of Travel,' edited by A. Murray, vol. i. 1868, p. 286. 



