Subordinate also to this natural selection is the principle that bright
colour and other special qualities may be developed in the males of a
race, because individuals with such advantages are more attractive, and
therefore more easily find mates, than dull-coloured or otherwise less
attractive individuals.

Of each of these principles I may give a simple example. Supposing a
species of bird with a soft slender beak to be placed on an island,
where the only food they could obtain was fruit enclosed in a hard or
tough shell or covering. Supposing some birds accidentally possessed of
a beak that was shorter and stouter than the others', these would be
able to break open the shell and get at the fruit, while the others
would starve. Some of the descendants of the birds with the stout beaks
would inherit the same peculiarity, and in the course of several
generations there would thus arise a species with short and strong,
perhaps curved, beaks just fitted to live on fruits of the kind
described. In a similar way the webbed feet of birds that swim were
developed by their aquatic habits. And so with the long slender toes of
the waders, which are so well fitted for walking over floating aquatic
plants.

Of the other principle, sexual selection, a familiar example is the
bright and showy colouring of the male birds of many species: the
females of their species, as they need protection while helplessly
sitting on their eggs, are dull-coloured like the bark of trees or the
sand, among which their nests lie hid.

Some of the Himalayan pheasants exhibit this peculiarity to a marked
degree. Originally, it is said, the male bird, which was more brightly