The Descent of Man

any one hearing it for the first time. As this jarring
sound is made chiefly during the breeding-season,
it has been considered as a lovesong;
but it is perhaps more strictly a love- call.
The female, when driven from her nest, has
been observed thus to call her mate, who answered
in the same manner and soon appeared.
Lastly, the male hoopoe (Upupa epops) combines
vocal and instrumental music; for during
the breeding-season this bird, as Mr. Swinhoe
observed, first draws in air, and then taps the
end of its beak perpendicularly down against a
stone or the trunk of a tree, "when the breath
being forced down the tubular bill produces the
correct sound." If the beak is not thus struck
against some object, the sound is quite different.
Air is at the same time swallowed, and the
oesophagus thus becomes much swollen; and
this probably acts as a resonator, not only with
the hoopoe, but with pigeons and other birds.
(52. For the foregoing facts see, on Birds of Paradise,
Brehm, 'Thierleben,' Band iii. s. 325. On