The Descent of Man

strengthened by what Malherbe states with
respect to Indopicus carlotta; namely, that the
young females, like the young males, have some
crimson about their heads, but that this colour
disappears in the adult female, whilst it is
intensified in the adult male. Nevertheless the
following considerations render this view extremely
doubtful: the male takes a fair share in
incubation (26. Audubon's 'Ornithological Biography,'
vol. ii. p. 75; see also the 'Ibis,' vol. i. p.
268.), and would be thus almost equally exposed
to danger; both sexes of many species have
their heads of an equally bright crimson; in
other species the difference between the sexes
in the amount of scarlet is so slight that it can
hardly make any appreciable difference in the
danger incurred; and lastly, the colouring of the
head in the two sexes often differs slightly in
other ways.
The cases, as yet given, of slight and graduated
differences in colour between the males and