The Descent of Man

lack-cock certainly serves as a call to the female,
for it has been known to bring four or five
females from a distance to a male under confinement;
but as the black-cock continues his spel
for hours during successive days, and in the
case of the capercailzie "with an agony of passion,"
we are led to suppose that the females
which are present are thus charmed. (50. L.
Lloyd, 'The Game Birds of Sweden,' etc., 1867,
pp. 22, 81.) The voice of the common rook is
known to alter during the breeding-season, and
is therefore in some way sexual. (51. Jenner,
'Philosophical Transactions,' 1824, p. 20.) But
what shall we say about the harsh screams of,
for instance, some kinds of macaws; have these
birds as bad taste for musical sounds as they
apparently have for colour, judging by the inharmonious
contrast of their bright yellow and
blue plumage? It is indeed possible that without
any advantage being thus gained, the loud
voices of many male birds may be the result of
the inherited effects of the continued use of