produced is audible at a considerable distance but cannot be described;
and I feel sure that its source would never be conjectured by 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 love-song; 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 Grouse, Richardson, Fauna Bor.
Americ.: Birds, pp. 343 and 359; Major W. Ross King, The Sportsman in
Canada, 1866, p. 156; Mr. Haymond, in Prof. Cox s Geol. Survey of
Indiana, p. 227; Audubon, American Ornitholog. Biograph. vol. i. p.
216. On the Kalij-pheasant, Jerdon, Birds of India, vol. iii. p. 533.
On the Weavers, Livingstone s Expedition to the Zambesi, 1865, p.
425. On Woodpeckers, Macgillivray, Hist. of British Birds, vol. iii.
1840, pp. 84, 88, 89, and 95. On the Hoopoe, Mr. Swinhoe, in Proc.
Zoolog. Soc. June 23, 1863 and 1871, p. 348. On the Night-jar,
Audubon, ibid. vol. ii. p. 255, and American Naturalist, 1873, p.
672. The English Night-jar likewise makes in the spring a curious noise
during its rapid flight.)
[Fig. 41. Outer tail-feather of Scolopax gallinago (from Proc. Zool.
Soc. 1858).
Fig. 42. Outer tail-feather of Scolopax frenata.
Fig. 43. Outer tail-feather of Scolopax javensis.]
In the foregoing cases sounds are made by the aid of structures already
present and otherwise necessary; but in the following cases certain
feathers have been specially modified for the express purpose of
producing sounds. The drumming, bleating, neighing, or thundering noise
402