the vocal organs of the two sexes, although the males of most species
sing so much better and more continuously than the females.
It is remarkable that only small birds properly sing. The Australian
genus Menura, however, must be excepted; for the Menura Alberti, which
is about the size of a half-grown turkey, not only mocks other birds,
but its own whistle is exceedingly beautiful and varied. The males
congregate and form corroborying places, where they sing, raising and
spreading their tails like peacocks, and drooping their wings. (39.
Gould, Handbook to the Birds of Australia, vol. i. 1865, pp. 308-310.
See also Mr. T.W. Wood in the Student, April 1870, p. 125.) It is
also remarkable that birds which sing well are rarely decorated with
brilliant colours or other ornaments. Of our British birds, excepting
the bullfinch and goldfinch, the best songsters are plain-coloured. The
kingfisher, bee-eater, roller, hoopoe, woodpeckers, etc., utter harsh
cries; and the brilliant birds of the tropics are hardly ever
songsters. (40. See remarks to this effect in Gould s Introduction to
the Trochilidae, 1861, p. 22.) Hence bright colours and the power of
song seem to replace each other. We can perceive that if the plumage
did not vary in brightness, or if bright colours were dangerous to the
species, other means would be employed to charm the females; and melody
of voice offers one such means.
[Fig. 39. Tetrao cupido: male. (T.W. Wood.)]
In some birds the vocal organs differ greatly in the two sexes. In the
Tetrao cupido (Fig. 39) the male has two bare, orange-coloured sacks,
one on each side of the neck; and these are largely inflated when the
male, during the breeding-season, makes his curious hollow sound,
audible at a great distance. Audubon proved that the sound was
intimately connected with this apparatus (which reminds us of the
air-sacks on each side of the mouth of certain male frogs), for he
found that the sound was much diminished when one of the sacks of a
tame bird was pricked, and when both were pricked it was altogether
stopped. The female has a somewhat similar, though smaller naked space
of skin on the neck; but this is not capable of inflation. (41. The
Sportsman and Naturalist in Canada, by Major W. Ross King, 1866, pp.
144-146. Mr. T.W. Wood gives in the Student (April 1870, p. 116) an
excellent account of the attitude and habits of this bird during its
courtship. He states that the ear-tufts or neck-plumes are erected, so
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