The Descent of Man

sexual difference in the length and curvature of
the bronchi. (48. 'Elements of Comparative
Anatomy,' by R. Wagner, Eng. translat. 1845, p.
111. With respect to the swan, as given above,
Yarrell's 'History of British Birds,' 2nd edition,
1845, vol. iii. p. 193.) Highly important structures
have, therefore, in these cases been modified
according to sex.
It is often difficult to conjecture whether the
many strange cries and notes uttered by male
birds during the breeding-season serve as a
charm or merely as a call to the female. The soft
cooing of the turtle-dove and of many pigeons,
it may be presumed, pleases the female. When
the female of the wild turkey utters her call in
the morning, the male answers by a note which
differs from the gobbling noise made, when
with erected feathers, rustling wings and distended
wattles, he puffs and struts before her.
(49. C.L. Bonaparte, quoted in the 'Naturalist
Library: Birds,' vol. xiv. p. 126.) The spel of the