The Descent of Man, Charles Darwin [top 100 books of all time checklist txt] 📗

fight at all times; and the males of the capercailzie sometimes hold their Balzen or leks at the usual place of assemblage during the autumn. (34. L. Lloyd, ‘Game Birds of Sweden,’ 1867, p. 25.) Hence it is not at all surprising that male birds should continue singing for their own amusement after the season for courtship is over.

As shewn in a previous chapter, singing is to a certain extent an art, and is much improved by practice. Birds can be taught various tunes, and even the unmelodious sparrow has learnt to sing like a linnet. They acquire the song of their foster parents (35. Barrington, ibid. p. 264, Bechstein, ibid. s. 5.), and sometimes that of their neighbours. (36. Dureau de la Malle gives a curious instance (‘Annales des Sc. Nat.’ 3rd series, Zoolog., tom. x. p. 118) of some wild blackbirds in his garden in Paris, which naturally learnt a republican air from a caged bird.) All the common songsters belong to the Order of Insessores, and their vocal organs are much more complex than those of most other birds; yet it is a singular fact that some of the Insessores, such as ravens, crows, and magpies, possess the proper apparatus (37. Bishop, in ‘Todd’s Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1496.), though they never sing, and do not naturally modulate their voices to any great extent. Hunter asserts (38. As stated by Barrington in ‘Philosophical Transactions,’ 1773, p. 262.) that with the true songsters the muscles of the larynx are stronger in the males than in the females; but with this slight exception there is no difference in 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 that they meet over the crown of the head. See his drawing, Fig. 39.) The male of another kind of grouse (Tetrao urophasianus), whilst courting the female, has his “bare yellow oesophagus inflated to a prodigious size, fully half as large as the body”; and he then utters various grating, deep, hollow tones. With his neck-feathers erect, his wings lowered, and buzzing on the ground, and his long pointed tail spread out like a fan, he displays a variety of grotesque attitudes. The oesophagus of the female is not in any way remarkable. (42. Richardson, ‘Fauna Bor. American: Birds,’ 1831, p. 359. Audubon, ibid. vol. iv. p. 507.)

[Fig. 40. The Umbrella-bird or Cephalopterus ornatus, male (from Brehm).]

It seems now well made out that the great throat pouch of the European male bustard (Otis tarda), and of at least four other species, does not, as was formerly supposed, serve to hold water, but is connected with the utterance during the breeding-season of a peculiar sound resembling “oak.” (43. The following papers have been lately written on this subject: Prof. A. Newton, in the ‘Ibis,’ 1862, p. 107; Dr. Cullen, ibid. 1865, p. 145; Mr. Flower, in ‘Proc. Zool. Soc.’ 1865, p. 747; and Dr. Murie, in ‘Proc. Zool. Soc.’ 1868, p. 471. In this latter paper an excellent figure is given of the male Australian Bustard in full display with the sack distended. It is a singular fact that the sack is not developed in all the males of the same species.) A crow-like bird inhabiting South America (see Cephalopterus ornatus, Fig. 40) is called the umbrella-bird, from its immense top knot, formed of bare white quills surmounted by dark-blue plumes, which it can elevate into a great dome no less than five inches in diameter, covering the whole head. This bird has on its neck a long, thin, cylindrical fleshy appendage, which is thickly clothed with scale-like blue feathers. It probably serves in part as an ornament, but likewise as a resounding apparatus; for Mr. Bates found that it is connected “with an unusual development of the trachea and vocal organs.” It is dilated when the bird utters its singularly deep, loud and long sustained fluty note. The head- crest and neck-appendage are rudimentary in the female. (44. Bates, ‘The Naturalist on the Amazons,’ 1863, vol. ii. p. 284; Wallace, in ‘Proceedings, Zoological Society,’ 1850, p. 206. A new species, with a still larger neck-appendage (C. penduliger), has lately been discovered, see ‘Ibis,’ vol. i. p. 457.)

The vocal organs of various web-footed and wading birds are extraordinarily complex, and differ to a certain extent in the two sexes. In some cases the trachea is convoluted, like a French horn, and is deeply embedded in the sternum. In the wild swan (Cygnus ferus) it is more deeply embedded in the adult male than in the adult female or young male. In the male Merganser the enlarged portion of the trachea is furnished with an additional pair of muscles. (45. Bishop, in Todd’s ‘Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1499.) In one of the ducks, however, namely Anas punctata, the bony enlargement is only a little more developed in the male than in the female. (46. Prof. Newton, ‘Proc. Zoolog. Soc.’ 1871, p. 651.) But the meaning of these differences in the trachea of the two sexes of the Anatidae is not understood; for the male is not always the more vociferous; thus with the common duck, the male hisses, whilst the female utters a loud quack. (47. The spoonbill (Platalea) has its trachea convoluted into a figure of eight, and yet this bird (Jerdon, ‘Birds of India,’ vol. iii. p. 763) is mute; but Mr. Blyth informs me that the convolutions are not constantly present, so that perhaps they are now tending towards abortion.) In both sexes of one of the cranes (Grus virgo) the trachea penetrates the sternum, but presents “certain sexual modifications.” In the male of the black stork there is also a well-marked 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 black-cock certainly serves as a call to the female, for it has been known to bring four or five females from a distance to a male under confinement; but as the black-cock continues his spel for hours during successive days, and in the case of the capercailzie “with an agony of passion,” we are led to suppose that the females which are present are thus charmed. (50. L. Lloyd, ‘The Game Birds of Sweden,’ etc., 1867, pp. 22, 81.) The voice of the common rook is known to alter during the breeding-season, and is therefore in some way sexual. (51. Jenner, ‘Philosophical Transactions,’ 1824, p. 20.) But what shall we say about the harsh screams of, for instance, some kinds of macaws; have these birds as bad taste for musical sounds as they apparently have for colour, judging by the inharmonious contrast of their bright yellow and blue plumage? It is indeed possible that without any advantage being thus gained, the loud voices of many male birds may be the result of the inherited effects of the continued use of their vocal organs when excited by the strong passions of love, jealousy and rage; but to this point we shall recur when we treat of quadrupeds.

We have as yet spoken only of the voice, but the males of various birds practise, during their courtship, what may be called instrumental music. Peacocks and Birds of Paradise rattle their quills together. Turkey-cocks scrape their wings against the ground, and some kinds of grouse thus produce a buzzing sound. Another North American grouse, the Tetrao umbellus, when with his tail erect, his ruffs displayed, “he shows off his finery to the females, who lie hid in the neighbourhood,” drums by rapidly striking his wings together above his back, according to Mr. R. Haymond, and not, as Audubon thought, by striking them against his sides. The sound thus produced is compared by some to distant thunder, and by others to the quick roll of a drum. The female never drums, “but flies directly to the place where the male is thus engaged.” The male of the Kalij-pheasant, in the Himalayas, often makes a singular drumming noise with his wings, not unlike the sound produced by shaking a stiff piece of cloth.” On the west coast of Africa the little