230 
SEXUAL SELECTION: BIEDS. 
Fart II. 
As sexual selection depends on so fluctuating an 
element as taste, we can understand flow it is tflat witli- 
in tfle same group of birds, witfl flabits of life nearly 
tfle 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. Piebald 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 colour is agreeable to birds, we 
may conclude, by looking through any large collection 
of specimens or series of coloured plates, for the sexes 
frequently differ from each other in the male having 
the pale parts of a purer white, and the variously 
coloured 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 object and an aim in Nature.’’ 
I wish the Duke had explained 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 notion 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 example; the males 
many otlier species are black. This fact supports the conjecture that 
these conspicuous colours may aid the sexes in finding each other during 
the breeding-season. 
56 ‘ The Journal of Travel,’ edited by A. Murray, vol. i. 1868, p. 286. 
