The Descent of Man

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, for the sexes often 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 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-coloured 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. (55. See Jerdon on
the genus Palaeornis, 'Birds of India,' vol. i. pp.
258-260.) As so many male birds have elonga-