BIRDS-CONSPICUOUS COLORS. 489 



discovers and flies down to a carcass floating on the sea or cast 

 up on the beach, will be seen from a great distance, and will 

 guide other birds of the same and other species, to the prey; but 

 as this would be a disadvantage to the first finders, the individuals 

 which were the whitest or blackest would not thus procure more 

 food than the less strongly colored individuals. Hence conspicu- 

 ous colors cannot have been gradually acquired for this purpose 

 through natural selection. 



As sexual selection depends on so fluctuating an element 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, storks, ibises, swans, 

 terns, and petrels. Piebald birds likewise 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 in- 

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

 stead of a plum-blue head.'° As so many male birds have elon- 

 gated 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 lilie 

 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 appre- 

 ciated for the sake of novelty. The young of the Ardea asha are 

 white, the adults being dark slate colored; and not only the 

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

 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 



^' See Jerflon on the genus Palaeornis, 'Birds of India," vol. 1. p. 



