562 THE DESCENT OF MAN. 



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

 group of birds having nearly the same habits, there should 

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

 species for instance, both white and black cockatoos, 

 gtprks, ibises, swans, terns and petrels. Piebald birds like- 

 wise sometimes occur in the same groups together with 

 black and white species; for instance, the black-necked 

 swan, certain terns and the common magpie. That a strong 

 contrast in color is agreeable to birds we may conclude by 

 looking through any large collection, for the sexes often 

 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 the female. 



It would even appear that mere novelty, or slight 

 changes for the sake of change, have sometimes acted on 

 female birds as a charm, like changes of fashion with us. 

 Thus the males of some parrots can hardly be said to be 

 more beautiful than the females, at least according to our 

 taste, but they differ in such points, as in having a rose- 

 colored collar instead of "a bright, emeraldine, narrow 

 green collar;" or in the male having a black collar instead 

 of "a yellow demi-collar in front," with a pale roseate 

 instead of a plum-blue head.* As so many male birds 

 have elongated tail-feathers or elongated crests for their 

 chief ornament, the shortened tail, formerly described in 

 the male of a humming-bird, and the shortened crest of 

 the male goosander, seem like one of the many changes of 

 fashion which we admire in our own dresses. 



Some members of the heron family offer a still more 

 curious case of novelty in coloring, having, as it appears, 

 been appreciated for the sake of novelty. The young of 

 the Ardea aslia are white, the adults being dark slate- 

 colored; and not only the young, but the adults in their 

 winter plumage, of the allied Buplius coromandiis are 

 white, this color changing into a rich golden-buff during 

 the breeding-season. It is incredible that the young of 

 these two species, as well as of some other members of the 

 same family, f should for any special purpose have been 



*See Jerdon on the genus Palaeornis, " Birds of India," vol. i, pp, 

 258-260. 



fThe young of Ardea rufescens and A. c&rulea of the United 

 States are likewise white, the adults being colored in accordance 



