688 THE DESCENT OF MAN 



feathers or elongated crests for their chief ornament, the 

 shortened tail, formerly described in the male of a hum- 

 ming-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 asha are white, the adults being dark slate-col- 

 ored; and not only the young, but the adults in their win- 

 ter plumage, of the allied Buphus coromandus 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," should for any special purpose have been ren- 

 dered pure white and thus made conspicuous to their en- 

 emies; or that the adults of one of these two species should 

 have been specially rendered white during the winter in a 

 country which is never covered with snow. On the other 

 hand, we have good reason to believe that whiteness has 

 been gained by many birds as a sexual ornament. We 

 may, therefore, conclude that some early progenitor of the 

 Ardea asha and the Buphus acquired a white plumage 

 for nuptial purposes, and transmitted this color to their 

 young; so that the young and the old became white like 

 certain existing egrets; and that the whiteness was after- 

 ward retained by the young, while it was exchanged by 

 the adults for more strongly pronounced tints. But if we 

 could look still further back to the still earlier progenitors 

 of these two species, we should probably see the adults 

 dark colored. I infer that this would be the case from 

 the analogy of many other birds, which are dark while 



" The young of Ardea rufescens and A. ccerulea of the TTnited States are 

 Kkewise white, the adults being colored in accordance with their specific names. 

 Audubon ("Ornith. Biography," vol. iii. p. 416; vol. iv. p. 58) seems ralher 

 pleased at the thought that this remarkable change of plumage will greatly 

 "disconcert the systematists." 



