Man In The Modern World

MAN IN THE MODERN WORLD
bird, the ruff (Machetes). In the winter the sexes are only to be told
apart by size, but in the breeding season the males grow a magnificent
ruff—a tippet or collar—round the cheeks and neck, and two fine
ear-tufts above. What is more, it is hard to find two males alike; not
only do they develop different ground-colours in their plumage, but
the collar and ear-tufts may either or both be of some special colour
or marking, one black, the other white; or chestnut, pepper and salt,
buff, sandy, grey, sepia, and what not. Arrived at their breeding
places, the males assemble at a definite spot, usually known as a
'hill,' though it may be but a dry area in the marsh. The females
visit the hill from time to time, but the males never go near the nests
out in the marshes, nor take any share in brooding or the cares of the
young. On the hill each male usually keeps to a little private area of
his own. When no females are present, the male birds will be dancing,
whirring round like Dervishes, and sparring and jousting with each
other. On the arrival of a female, the scene is changed. The males
crouch down, immobile, sometimes flat on the ground with spread
wings. The hen may simply stroll round and fly away again—on
which the cock birds rise rather sheepishly from their prostrate pos-
ture, as if pretending that nothing had been going on. Or she may
approach a male and nibble at his neck, on which mating is con-
summated.
Edmund Selous watched one particular ruff hill in Holland for
weeks, arriving at his hide at or before dawn. Every male on the hill
was distinguishable by his appearance; and so Selous was able to
discover that some were more successful than others,
Here is Darwin's theory in practice, working itself out in every
detail—the adornments developed only by the male in the breeding
season, and used only in sexual combat and sexual display; the male
with no power to enforce his desires, the female completely arbiter of
her choice; and, finally, the evidence that choice is exercised. The
only puzzling point is the extreme variability of the males. This may
be explained by some later discoveries. Various biologists, as we
shall see later, have found that display, combat, and threat have a
direct physiological effect on birds of both sexes, actually helping to
ripen the reproductive organs. And Fraser Darling and others have
recently shown that this effect is cumulative, some stimulus resulting
from the sight of other birds courting or fighting. This at once ex-
plains the frequent occurrence of communal display-grounds: they
are arrangements for heightening reproductive efficiency. But it also
explains the ruff's variability. If, as seems reasonable, the unfamiliar
is more exciting than the familiar, variety will have a greater mass-
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