488 THE DESCENT OF MAN 



duces tlie correct sound. ' ' If tlie beak is not thus struck 

 against some object, tbe 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. " 



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 

 (as expressed by different observers) made by the com- 

 mon snipe [Scolopax gallinago) must have surprised every 

 one who has ever heard it. This bird, during the pairing 

 season, flies to "perhaps a thousand feet in height," and 



St-..' — -R 



Pig. 41.— Outer taU-feather of Scolopax gallinago (from "Proo. Zool. See," 1858). 



after zigzagging about for a time descends to the earth in a 

 curved line, with outspread tail and quivering pinions, and 

 surprising velocity. The sound is emitted only during this 

 rapid descent. No one was able to explain the cause, until 

 M. Meves observed that on each side of the tail the outer 

 feathers are peculiarly formed (Fig. 41), having a stiff 

 sabre-shaped shaft, with the oblique barbs of unusual length, 

 the outer webs being strongly bound together. He found 



'^ For the foregoing facts see, on Birds of Paradise, Brehm, "TMerleBen, " 

 Band iii. s. 325. On G-rouse, Richardson, "Fauna Bor. Americ. : Birds," pp. 

 343 and 359; Major W. Boss King, "The Sportsman in Canada," 1866, p. 156; 

 Mr. Haymond, in Prof. Cox's "Geol. Survey of Indiana," p. 22t; Audubon, 

 "American Ornitholog. Biograph.," vol. i. p. 216. On the Kalij-pheasant, Jer- 

 don, "Birds of India," vol. iii. p. 533. On the Weavers, "Livingstone's Ex- 

 pedition 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. 

 Swiuhoe, in "Proo. 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. 



