Figure 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.)

Figure 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 black-weavers (Ploceus?) congregate in a small party on the bushes round a small open space, and sing and glide through the air with quivering wings, “which make a rapid whirring sound like a child’s rattle.” One bird after another thus performs for hours together, but only during the courting-season. At this season, and at no other time, the males of certain night-jars (Caprimulgus) make a strange booming noise with their wings. The various species of woodpeckers strike a sonorous branch with their beaks, with so rapid a vibratory movement that “the head appears to be in two places at once.” The sound thus 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.)

Figure 41: Outer tail-feather of Scolopax gallinago (from ‘Proc. Zool. Soc.’ 1858).

Figure 42: Outer tail-feather of Scolopax frenata.

Figure 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 (as expressed by different observers) made by the common 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 after zig-zagging 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 that by blowing on these feathers, or by fastening them to a long thin stick and waving them rapidly through the air, he could reproduce the drumming noise made by the living bird. Both sexes are furnished with these feathers, but they are generally larger in the male than in the female, and emit a deeper note. In some species, as in S. frenata (Fig. 42), four feathers, and in S. javensis (Fig. 43), no less than eight on each side of the tail are greatly modified. Different tones are emitted by the feathers of the different species when waved through the air; and the Scolopax Wilsonii of the United States makes a switching noise whilst descending rapidly to the earth. (53. See M. Meves’ interesting paper in ‘Proc. Zool. Soc.’ 1858, p. 199. For the habits of the snipe, Macgillivray, ‘History of British Birds,’ vol. iv. p. 371. For the American snipe, Capt. Blakiston, ‘Ibis,’ vol. v. 1863, p. 131.)

Figure 44: Primary wing-feather of a Humming-bird, the Selasphorus platycercus (from a sketch by Mr. Salvin).
Upper figure, that of male;
lower figure, corresponding feather of female.

In the male of the Chamaepetes unicolor (a large gallinaceous bird of America), the first primary wing-feather is arched towards the tip and is much more attenuated than in the female. In an allied bird, the Penelope nigra, Mr. Salvin observed a male, which, whilst it flew downwards “with outstretched wings, gave forth a kind of crashing rushing noise,” like the falling of a tree. (54. Mr. Salvin, in ‘Proceedings, Zoological Society,’ 1867, p. 160. I am much indebted to this distinguished ornithologist for sketches of the feathers of the Chamaepetes, and for other information.) The male alone of one of the Indian bustards (Sypheotides auritus) has its primary wing-feathers greatly acuminated; and the male of an allied species is known to make a humming noise whilst courting the female. (55. Jerdon, ‘Birds of India,’ vol. iii. pp. 618, 621.) In a widely different group of birds, namely Humming-birds, the males alone of certain kinds have either the shafts of their primary wing-feathers broadly dilated, or the webs abruptly excised towards the extremity. The male, for instance, of Selasphorus platycercus, when adult, has the first primary wing-feather (Fig. 44), thus excised. Whilst flying from flower to flower he makes “a shrill, almost whistling noise” (56. Gould, ‘Introduction to the Trochilidae,’ 1861, p. 49. Salvin, ‘Proceedings, Zoological Society,’ 1867, p. 160.); but it did not appear to Mr. Salvin that the noise was intentionally made.

Figure 45: Secondary wing-feathers of Pipra deliciosa (from Mr. Sclater, in ‘Proc. Zool. Soc.’ 1860).
The three upper feathers, a, b, c, from the male;
the three lower corresponding feathers, d, e, f, from the female.
a and d, fifth secondary wing-feather of male and female, upper surface.
b and e, sixth secondary, upper surface.
c and f, seventh secondary, lower surface.

Lastly, in several species of a sub-genus of Pipra or Manakin, the males, as described by Mr. Sclater, have their secondary wing-feathers modified in a still more remarkable manner. In the brilliantly-coloured P. deliciosa the first three secondaries are thick-stemmed and curved towards the body; in the fourth and fifth (Fig. 45, a) the change is greater; and in the sixth and seventh (b, c) the shaft “is thickened to an extraordinary degree, forming a solid horny lump.” The barbs also are greatly changed in shape, in comparison with the corresponding feathers (d, e, f) in the female. Even the bones of the wing, which support these singular feathers in the male, are said by Mr. Fraser to be much thickened. These little birds make an extraordinary noise, the first “sharp note being not unlike the crack of a whip.” (57. Sclater, in ‘Proceedings, Zoological Society,’ 1860, p. 90, and in ‘Ibis,’ vol. iv. 1862, p. 175. Also Salvin, in ‘Ibis,’ 1860, p. 37.)

The diversity of the sounds, both vocal and instrumental, made by the males of many birds during the breeding-season, and the diversity of the means for producing such sounds, are highly remarkable. We thus gain a high idea of their importance for sexual purposes, and are reminded of the conclusion arrived at as to insects. It is not difficult to imagine the steps by which the notes of a bird, primarily used as a mere call or for some other purpose, might have been improved into a melodious love song. In the case of the modified feathers, by which the drumming, whistling, or roaring noises are produced, we know that some birds during their courtship flutter, shake, or rattle their unmodified feathers together; and if the females were led to select the best performers, the males which possessed the strongest or thickest, or most attenuated feathers, situated on any part of the body, would be the most successful; and thus by slow degrees the feathers might be modified to almost any extent. The females, of course, would not notice each slight successive alteration in shape, but only the sounds thus produced. It is a curious fact that in the same class of animals, sounds so different as the drumming of the snipe’s tail, the tapping of the woodpecker’s beak, the harsh trumpet-like cry of certain water-fowl, the cooing of the turtle-dove, and the song of the nightingale, should all be pleasing to the females of the several species. But we must not judge of the tastes of distinct species by a uniform standard; nor must we judge by the standard of man’s taste. Even with man, we should remember what discordant noises, the beating of tom-toms and the shrill notes of reeds, please the ears of savages. Sir S. Baker remarks (58. ‘The Nile Tributaries of Abyssinia,’ 1867, p. 203.), that “as the stomach of the Arab prefers the raw meat and reeking liver taken hot from the animal, so does his ear prefer his equally coarse and discordant music to all other.”

With birds the voice serves to express various emotions, such as distress, fear, anger, triumph, or mere happiness. It is apparently sometimes used to excite terror, as in the case of the hissing noise made by some nestling-birds. Audubon (25. ‘Ornithological Biography,’ vol. v. p. 601.), relates that a night-heron (Ardea nycticorax, Linn.), which he kept tame, used to hide itself when a cat approached, and then “suddenly start up uttering one of the most frightful cries, apparently enjoying the cat’s alarm and flight.” The common domestic cock clucks to the hen, and the hen to her chickens, when a dainty morsel is found. The hen, when she has laid an egg, “repeats the same note very often, and concludes with the sixth above, which she holds for a longer time” (26. The Hon. Daines Barrington, ‘Philosophical Transactions,’ 1773, p. 252.); and thus she expresses her joy. Some social birds apparently call to each other for aid; and as they flit from tree to tree, the flock is kept together by chirp answering chirp. During the nocturnal migrations of geese and other water-fowl, sonorous clangs from the van may be heard in the darkness overhead, answered by clangs in the rear. Certain cries serve as danger signals, which, as the sportsman knows to his cost, are understood by the same species and by others. The domestic cock crows, and the humming-bird chirps, in triumph over a defeated rival. The true song, however, of most birds and various strange cries are chiefly uttered during the breeding-season, and serve as a charm, or merely as a call-note, to the other sex.

Naturalists are much divided with respect to the object of the singing of birds. Few more careful observers ever lived than Montagu, and he maintained that the “males of song-birds and of many others do not in general search for the female, but, on the contrary, their business in the spring is to perch on some conspicuous spot, breathing out their full and armorous notes, which, by instinct, the female knows, and repairs to the spot to choose her mate.” (27. ‘Ornithological Dictionary,’ 1833, p. 475.) Mr. Jenner Weir informs me that this is certainly the case with the nightingale. Bechstein, who kept birds during his whole life, asserts, “that the female canary always chooses the best singer, and that in a state of nature the female finch selects that male out of a hundred whose notes please her most.” (28. ‘Naturgeschichte der Stubenvogel,’ 1840, s. 4. Mr. Harrison Weir likewise writes to me:–“I am informed that the best singing males generally get a mate first, when they are bred in the same room.”) There can be no doubt that birds closely attend to each other’s song. Mr. Weir has told me of the case of a bullfinch which had been taught to pipe a German waltz, and who was so good a performer that he cost ten guineas; when this bird was first introduced into a room where other birds were kept and he began to sing, all the others, consisting of about twenty linnets and canaries, ranged themselves on the nearest side of their cages, and listened with the greatest interest to the new performer. Many naturalists believe that the singing of birds is almost exclusively “the effect of rivalry and emulation,” and not for the sake of charming their mates. This was the opinion of Daines Barrington and White of Selborne, who both especially attended to this subject. (29. ‘Philosophical Transactions,’ 1773, p. 263. White’s ‘Natural History of Selborne,’ 1825, vol. i. p. 246.) Barrington, however, admits that “superiority in song gives to birds an amazing ascendancy over others, as is well known to bird-catchers.”

It is certain that there is an intense degree of rivalry between the males in their singing. Bird-fanciers match their birds to see which will sing longest; and I was told by Mr. Yarrell that a first-rate bird will sometimes sing till he drops down almost dead, or according to Bechstein (30. ‘Naturgesch. der Stubenvogel,’ 1840, s. 252.), quite dead from rupturing a vessel in the lungs. Whatever the cause may be, male birds, as I hear from Mr. Weir, often die suddenly during the season of song. That the habit of singing is sometimes quite independent of love is clear, for a sterile, hybrid canary-bird has been described (31. Mr. Bold, ‘Zoologist,’ 1843-44, p. 659.) as singing whilst viewing itself in a mirror, and then dashing at its own image; it likewise attacked with fury a female canary, when put into the same cage. The jealousy excited by the act of singing is constantly taken advantage of by bird-catchers; a male, in good song, is hidden and protected, whilst a stuffed bird, surrounded by limed twigs, is exposed to view. In this manner, as Mr. Weir informs me, a man has in the course of a single day caught fifty, and in one instance, seventy, male chaffinches. The power and inclination to sing differ so greatly with birds that although the price of an ordinary male chaffinch is only sixpence, Mr. Weir saw one bird for which the bird-catcher asked three pounds; the test of a really good singer being that it will continue to sing whilst the cage is swung round the owner’s head.

That male birds should sing from emulation as well as for charming the female, is not at all incompatible; and it might have been expected that these two habits would have concurred, like those of display and pugnacity. Some authors, however, argue that the song of the male cannot serve to charm the female, because the females of some few species, such as of the canary, robin, lark, and bullfinch, especially when in a state of widowhood, as Bechstein remarks, pour forth fairly melodious strains. In some of these cases the habit of singing may be in part attributed to the females having been highly fed and confined (32. D. Barrington, ‘Philosophical Transactions,’ 1773, p. 262. Bechstein, ‘Stubenvogel,’ 1840, s. 4.), for this disturbs all the functions connected with the reproduction of the species. Many instances have already been given of the partial transference of secondary masculine characters to the female, so that it is not at all surprising that the females of some species should possess the power of song. It has also been argued, that the song of the male cannot serve as a charm, because the males of certain species, for instance of the robin, sing during the autumn. (33. This is likewise the case with the water-ouzel; see Mr. Hepburn in the ‘Zoologist,’ 1845-46, p. 1068.) But nothing is more common than for animals to take pleasure in practising whatever instinct they follow at other times for some real good. How often do we see birds which fly easily, gliding and sailing through the air obviously for pleasure? The cat plays with the captured mouse, and the cormorant with the captured fish. The weaver-bird (Ploceus), when confined in a cage, amuses itself by neatly weaving blades of grass between the wires of its cage. Birds which habitually fight during the breeding-season are generally ready to 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.

Figure 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.)

The males of many gallinaceous birds, especially of the polygamous kinds, are furnished with special weapons for fighting with their rivals, namely spurs, which can be used with fearful effect. It has been recorded by a trustworthy writer (11. Mr. Hewitt, in the ‘Poultry Book’ by Tegetmeier, 1866, p. 137.) that in Derbyshire a kite struck at a game-hen accompanied by her chickens, when the cock rushed to the rescue, and drove his spur right through the eye and skull of the aggressor. The spur was with difficulty drawn from the skull, and as the kite, though dead, retained his grasp, the two birds were firmly locked together; but the cock when disentangled was very little injured. The invincible courage of the game-cock is notorious: a gentleman who long ago witnessed the brutal scene, told me that a bird had both its legs broken by some accident in the cockpit, and the owner laid a wager that if the legs could be spliced so that the bird could stand upright, he would continue fighting. This was effected on the spot, and the bird fought with undaunted courage until he received his death-stroke. In Ceylon a closely allied, wild species, the Gallus Stanleyi, is known to fight desperately “in defence of his seraglio,” so that one of the combatants is frequently found dead. (12. Layard, ‘Annals and Magazine of Natural History,’ vol. xiv. 1854, p. 63.) An Indian partridge (Ortygornis gularis), the male of which is furnished with strong and sharp spurs, is so quarrelsome “that the scars of former fights disfigure the breast of almost every bird you kill.” (13. Jerdon, ‘Birds of India,’ vol. iii. p. 574.)

The males of almost all gallinaceous birds, even those which are not furnished with spurs, engage during the breeding-season in fierce conflicts. The Capercailzie and Black-cock (Tetrao urogallus and T. tetrix), which are both polygamists, have regular appointed places, where during many weeks they congregate in numbers to fight together and to display their charms before the females. Dr. W. Kovalevsky informs me that in Russia he has seen the snow all bloody on the arenas where the capercailzie have fought; and the black-cocks “make the feathers fly in every direction,” when several “engage in a battle royal.” The elder Brehm gives a curious account of the Balz, as the love-dances and love-songs of the Black-cock are called in Germany. The bird utters almost continuously the strangest noises: “he holds his tail up and spreads it out like a fan, he lifts up his head and neck with all the feathers erect, and stretches his wings from the body. Then he takes a few jumps in different directions, sometimes in a circle, and presses the under part of his beak so hard against the ground that the chin feathers are rubbed off. During these movements he beats his wings and turns round and round. The more ardent he grows the more lively he becomes, until at last the bird appears like a frantic creature.” At such times the black-cocks are so absorbed that they become almost blind and deaf, but less so than the capercailzie: hence bird after bird may be shot on the same spot, or even caught by the hand. After performing these antics the males begin to fight: and the same black-cock, in order to prove his strength over several antagonists, will visit in the course of one morning several Balz-places, which remain the same during successive years. (14. Brehm, ‘Thierleben,’ 1867, B. iv. s. 351. Some of the foregoing statements are taken from L. Lloyd, ‘The Game Birds of Sweden,’ etc., 1867, p. 79.)

The peacock with his long train appears more like a dandy than a warrior, but he sometimes engages in fierce contests: the Rev. W. Darwin Fox informs me that at some little distance from Chester two peacocks became so excited whilst fighting, that they flew over the whole city, still engaged, until they alighted on the top of St. John’s tower.

The spur, in those gallinaceous birds which are thus provided, is generally single; but Polyplectron (Fig. 51) has two or more on each leg; and one of the Blood-pheasants (Ithaginis cruentus) has been seen with five spurs. The spurs are generally confined to the male, being represented by mere knobs or rudiments in the female; but the females of the Java peacock (Pavo muticus) and, as I am informed by Mr. Blyth, of the small fire-backed pheasant (Euplocamus erythrophthalmus) possess spurs. In Galloperdix it is usual for the males to have two spurs, and for the females to have only one on each leg. (15. Jerdon, ‘Birds of India’: on Ithaginis, vol. iii. p. 523; on Galloperdix, p. 541.) Hence spurs may be considered as a masculine structure, which has been occasionally more or less transferred to the females. Like most other secondary sexual characters, the spurs are highly variable, both in number and development, in the same species.

Figure 38: Palamedea cornuta (from Brehm), shewing the double wing-spurs, and the filament on the head.

Various birds have spurs on their wings. But the Egyptian goose (Chenalopex aegyptiacus) has only “bare obtuse knobs,” and these probably shew us the first steps by which true spurs have been developed in other species. In the spur-winged goose, Plectropterus gambensis, the males have much larger spurs than the females; and they use them, as I am informed by Mr. Bartlett, in fighting together, so that, in this case, the wing-spurs serve as sexual weapons; but according to Livingstone, they are chiefly used in the defence of the young. The Palamedea (Fig. 38) is armed with a pair of spurs on each wing; and these are such formidable weapons that a single blow has been known to drive a dog howling away. But it does not appear that the spurs in this case, or in that of some of the spur-winged rails, are larger in the male than in the female. (16. For the Egyptian goose, see Macgillivray, ‘British Birds,’ vol. iv. p. 639. For Plectropterus, Livingstone’s ‘Travels,’ p. 254. For Palamedea, Brehm’s ‘Thierleben,’ B. iv. s. 740. See also on this bird Azara, ‘Voyages dans l’Amerique merid.’ tom. iv. 1809, pp. 179, 253.) In certain plovers, however, the wing-spurs must be considered as a sexual character. Thus in the male of our common peewit (Vanellus cristatus) the tubercle on the shoulder of the wing becomes more prominent during the breeding-season, and the males fight together. In some species of Lobivanellus a similar tubercle becomes developed during the breeding-season “into a short horny spur.” In the Australian L. lobatus both sexes have spurs, but these are much larger in the males than in the females. In an allied bird, the Hoplopterus armatus, the spurs do not increase in size during the breeding-season; but these birds have been seen in Egypt to fight together, in the same manner as our peewits, by turning suddenly in the air and striking sideways at each other, sometimes with fatal results. Thus also they drive away other enemies. (17. See, on our peewit, Mr. R. Carr in ‘Land and Water,’ Aug. 8th, 1868, p. 46. In regard to Lobivanellus, see Jerdon’s ‘Birds of India,’ vol. iii. p. 647, and Gould’s ‘Handbook of Birds of Australia,’ vol. ii. p. 220. For the Hoplopterus, see Mr. Allen in the ‘Ibis,’ vol. v. 1863, p. 156.)

The season of love is that of battle; but the males of some birds, as of the game-fowl and ruff, and even the young males of the wild turkey and grouse (18. Audubon, ‘Ornithological Biography,’ vol. ii. p. 492; vol. i. pp. 4-13.), are ready to fight whenever they meet. The presence of the female is the teterrima belli causa. The Bengali baboos make the pretty little males of the amadavat (Estrelda amandava) fight together by placing three small cages in a row, with a female in the middle; after a little time the two males are turned loose, and immediately a desperate battle ensues. (19. Mr. Blyth, ‘Land and Water,’ 1867, p. 212.) When many males congregate at the same appointed spot and fight together, as in the case of grouse and various other birds, they are generally attended by the females (20. Richardson on Tetrao umbellus, ‘Fauna Bor. Amer.: Birds,’ 1831, p. 343. L. Lloyd, ‘Game Birds of Sweden,’ 1867, pp. 22, 79, on the capercailzie and black-cock. Brehm, however, asserts (‘Thierleben,’ B. iv. s. 352) that in Germany the grey-hens do not generally attend the Balzen of the black-cocks, but this is an exception to the common rule; possibly the hens may lie hidden in the surrounding bushes, as is known to be the case with the gray-hens in Scandinavia, and with other species in N. America.), which afterwards pair with the victorious combatants. But in some cases the pairing precedes instead of succeeding the combat: thus according to Audubon (21. ‘Ornithological Biography,’ vol. ii. p. 275.), several males of the Virginian goat-sucker (Caprimulgus virgianus) “court, in a highly entertaining manner the female, and no sooner has she made her choice, than her approved gives chase to all intruders, and drives them beyond his dominions.” Generally the males try to drive away or kill their rivals before they pair. It does not, however, appear that the females invariably prefer the victorious males. I have indeed been assured by Dr. W. Kovalevsky that the female capercailzie sometimes steals away with a young male who has not dared to enter the arena with the older cocks, in the same manner as occasionally happens with the does of the red-deer in Scotland. When two males contend in presence of a single female, the victor, no doubt, commonly gains his desire; but some of these battles are caused by wandering males trying to distract the peace of an already mated pair. (22. Brehm, ‘Thierleben,’ etc., B. iv. 1867, p. 990. Audubon, ‘Ornithological Biography,’ vol. ii. p. 492.)

Even with the most pugnacious species it is probable that the pairing does not depend exclusively on the mere strength and courage of the male; for such males are generally decorated with various ornaments, which often become more brilliant during the breeding-season, and which are sedulously displayed before the females. The males also endeavour to charm or excite their mates by love-notes, songs, and antics; and the courtship is, in many instances, a prolonged affair. Hence it is not probable that the females are indifferent to the charms of the opposite sex, or that they are invariably compelled to yield to the victorious males. It is more probable that the females are excited, either before or after the conflict, by certain males, and thus unconsciously prefer them. In the case of Tetrao umbellus, a good observer (23. ‘Land and Water,’ July 25, 1868, p. 14.) goes so far as to believe that the battles of the male “are all a sham, performed to show themselves to the greatest advantage before the admiring females who assemble around; for I have never been able to find a maimed hero, and seldom more than a broken feather.” I shall have to recur to this subject, but I may here add that with the Tetrao cupido of the United States, about a score of males assemble at a particular spot, and, strutting about, make the whole air resound with their extraordinary noises. At the first answer from a female the males begin to fight furiously, and the weaker give way; but then, according to Audubon, both the victors and vanquished search for the female, so that the females must either then exert a choice, or the battle must be renewed. So, again, with one of the field-starlings of the United States (Sturnella ludoviciana) the males engage in fierce conflicts, “but at the sight of a female they all fly after her as if mad.” (24. Audubon’s ‘Ornithological Biography;’ on Tetrao cupido, vol. ii. p. 492; on the Sturnus, vol. ii. p. 219.)

• Sexual differences
• Law of battle
• Special weapons
• Vocal organs
• Instrumental music
• Love-antics and dances
• Decorations, permanent and seasonal
• Double and single annual moults
• Display of ornaments by the males.

Secondary sexual characters are more diversified and conspicuous in birds, though not perhaps entailing more important changes of structure, than in any other class of animals. I shall, therefore, treat the subject at considerable length. Male birds sometimes, though rarely, possess special weapons for fighting with each other. They charm the female by vocal or instrumental music of the most varied kinds. They are ornamented by all sorts of combs, wattles, protuberances, horns, air-distended sacks, top-knots, naked shafts, plumes and lengthened feathers gracefully springing from all parts of the body. The beak and naked skin about the head, and the feathers, are often gorgeously coloured. The males sometimes pay their court by dancing, or by fantastic antics performed either on the ground or in the air. In one instance, at least, the male emits a musky odour, which we may suppose serves to charm or excite the female; for that excellent observer, Mr. Ramsay (1. ‘Ibis,’ vol. iii. (new series), 1867, p. 414.), says of the Australian musk-duck (Biziura lobata) that “the smell which the male emits during the summer months is confined to that sex, and in some individuals is retained throughout the year; I have never, even in the breeding-season, shot a female which had any smell of musk.” So powerful is this odour during the pairing-season, that it can be detected long before the bird can be seen. (2. Gould, ‘Handbook of the Birds of Australia,’ 1865, vol. ii. p. 383.) On the whole, birds appear to be the most aesthetic of all animals, excepting of course man, and they have nearly the same taste for the beautiful as we have. This is shewn by our enjoyment of the singing of birds, and by our women, both civilised and savage, decking their heads with borrowed plumes, and using gems which are hardly more brilliantly coloured than the naked skin and wattles of certain birds. In man, however, when cultivated, the sense of beauty is manifestly a far more complex feeling, and is associated with various intellectual ideas.

Before treating of the sexual characters with which we are here more particularly concerned, I may just allude to certain differences between the sexes which apparently depend on differences in their habits of life; for such cases, though common in the lower, are rare in the higher classes. Two humming-birds belonging to the genus Eustephanus, which inhabit the island of Juan Fernandez, were long thought to be specifically distinct, but are now known, as Mr. Gould informs me, to be the male and female of the same species, and they differ slightly in the form of the beak. In another genus of humming-birds (Grypus), the beak of the male is serrated along the margin and hooked at the extremity, thus differing much from that of the female. In the Neomorpha of New Zealand, there is, as we have seen, a still wider difference in the form of the beak in relation to the manner of feeding of the two sexes. Something of the same kind has been observed with the goldfinch (Carduelis elegans), for I am assured by Mr. J. Jenner Weir that the bird-catchers can distinguish the males by their slightly longer beaks. The flocks of males are often found feeding on the seeds of the teazle (Dipsacus), which they can reach with their elongated beaks, whilst the females more commonly feed on the seeds of the betony or Scrophularia. With a slight difference of this kind as a foundation, we can see how the beaks of the two sexes might be made to differ greatly through natural selection. In some of the above cases, however, it is possible that the beaks of the males may have been first modified in relation to their contests with other males; and that this afterwards led to slightly changed habits of life.

Law of Battle

Almost all male birds are extremely pugnacious, using their beaks, wings, and legs for fighting together. We see this every spring with our robins and sparrows. The smallest of all birds, namely the humming-bird, is one of the most quarrelsome. Mr. Gosse (3. Quoted by Mr. Gould, ‘Introduction to the Trochilidae,’ 1861, page 29.) describes a battle in which a pair seized hold of each other’s beaks, and whirled round and round, till they almost fell to the ground; and M. Montes de Oca, in speaking or another genus of humming-bird, says that two males rarely meet without a fierce aerial encounter: when kept in cages “their fighting has mostly ended in the splitting of the tongue of one of the two, which then surely dies from being unable to feed.” (4. Gould, ibid. p. 52.) With waders, the males of the common water-hen (Gallinula chloropus) “when pairing, fight violently for the females: they stand nearly upright in the water and strike with their feet.” Two were seen to be thus engaged for half an hour, until one got hold of the head of the other, which would have been killed had not the observer interfered; the female all the time looking on as a quiet spectator. (5. W. Thompson, ‘Natural History of Ireland: Birds,’ vol. ii. 1850, p. 327.) Mr. Blyth informs me that the males of an allied bird (Gallicrex cristatus) are a third larger than the females, and are so pugnacious during the breeding-season that they are kept by the natives of Eastern Bengal for the sake of fighting. Various other birds are kept in India for the same purpose, for instance, the bulbuls (Pycnonotus hoemorrhous) which “fight with great spirit.” (6. Jerdon, ‘Birds of India,’ 1863, vol. ii. p. 96.)

Figure 37: The Ruff or Machetes pugnax (from Brehm’s ‘Thierleben’).

The polygamous ruff (Machetes pugnax, Fig. 37) is notorious for his extreme pugnacity; and in the spring, the males, which are considerably larger than the females, congregate day after day at a particular spot, where the females propose to lay their eggs. The fowlers discover these spots by the turf being trampled somewhat bare. Here they fight very much like game-cocks, seizing each other with their beaks and striking with their wings. The great ruff of feathers round the neck is then erected, and according to Col. Montagu “sweeps the ground as a shield to defend the more tender parts”; and this is the only instance known to me in the case of birds of any structure serving as a shield. The ruff of feathers, however, from its varied and rich colours probably serves in chief part as an ornament. Like most pugnacious birds, they seem always ready to fight, and when closely confined, often kill each other; but Montagu observed that their pugnacity becomes greater during the spring, when the long feathers on their necks are fully developed; and at this period the least movement by any one bird provokes a general battle. (7. Macgillivray, ‘History of British Birds,’ vol. iv. 1852, pp. 177-181.) Of the pugnacity of web-footed birds, two instances will suffice: in Guiana “bloody fights occur during the breeding-season between the males of the wild musk-duck (Cairina moschata); and where these fights have occurred the river is covered for some distance with feathers.” (8. Sir R. Schomburgk, in ‘Journal of Royal Geographic Society,’ vol. xiii. 1843, p. 31.) Birds which seem ill-adapted for fighting engage in fierce conflicts; thus the stronger males of the pelican drive away the weaker ones, snapping with their huge beaks and giving heavy blows with their wings. Male snipe fight together, “tugging and pushing each other with their bills in the most curious manner imaginable.” Some few birds are believed never to fight; this is the case, according to Audubon, with one of the woodpeckers of the United States (Picu sauratus), although “the hens are followed by even half a dozen of their gay suitors.” (9. ‘Ornithological Biography,’ vol. i. p. 191. For pelicans and snipes, see vol. iii. pp. 138, 477.)

The males of many birds are larger than the females, and this no doubt is the result of the advantage gained by the larger and stronger males over their rivals during many generations. The difference in size between the two sexes is carried to an extreme point in several Australian species; thus the male musk-duck (Biziura), and the male Cincloramphus cruralis (allied to our pipits) are by measurement actually twice as large as their respective females. (10. Gould, ‘Handbook of Birds of Australia,’ vol. i. p. 395; vol. ii. p. 383.) With many other birds the females are larger than the males; and, as formerly remarked, the explanation often given, namely, that the females have most of the work in feeding their young, will not suffice. In some few cases, as we shall hereafter see, the females apparently have acquired their greater size and strength for the sake of conquering other females and obtaining possession of the males.

The males of many gallinaceous birds, especially of the polygamous kinds, are furnished with special weapons for fighting with their rivals, namely spurs, which can be used with fearful effect. It has been recorded by a trustworthy writer (11. Mr. Hewitt, in the ‘Poultry Book’ by Tegetmeier, 1866, p. 137.) that in Derbyshire a kite struck at a game-hen accompanied by her chickens, when the cock rushed to the rescue, and drove his spur right through the eye and skull of the aggressor. The spur was with difficulty drawn from the skull, and as the kite, though dead, retained his grasp, the two birds were firmly locked together; but the cock when disentangled was very little injured. The invincible courage of the game-cock is notorious: a gentleman who long ago witnessed the brutal scene, told me that a bird had both its legs broken by some accident in the cockpit, and the owner laid a wager that if the legs could be spliced so that the bird could stand upright, he would continue fighting. This was effected on the spot, and the bird fought with undaunted courage until he received his death-stroke. In Ceylon a closely allied, wild species, the Gallus Stanleyi, is known to fight desperately “in defence of his seraglio,” so that one of the combatants is frequently found dead. (12. Layard, ‘Annals and Magazine of Natural History,’ vol. xiv. 1854, p. 63.) An Indian partridge (Ortygornis gularis), the male of which is furnished with strong and sharp spurs, is so quarrelsome “that the scars of former fights disfigure the breast of almost every bird you kill.” (13. Jerdon, ‘Birds of India,’ vol. iii. p. 574.)

The males of some, probably of many kinds of lizards, fight together from rivalry. Thus the arboreal Anolis cristatellus of S. America is extremely pugnacious: “During the spring and early part of the summer, two adult males rarely meet without a contest. On first seeing one another, they nod their heads up and down three or four times, and at the same time expanding the frill or pouch beneath the throat; their eyes glisten with rage, and after waving their tails from side to side for a few seconds, as if to gather energy, they dart at each other furiously, rolling over and over, and holding firmly with their teeth. The conflict generally ends in one of the combatants losing his tail, which is often devoured by the victor.” The male of this species is considerably larger than the female (65. Mr. N.L. Austen kept these animals alive for a considerable time; see ‘Land and Water,’ July 1867, p. 9.); and this, as far as Dr. Gunther has been able to ascertain, is the general rule with lizards of all kinds. The male alone of the Cyrtodactylus rubidus of the Andaman Islands possesses pre-anal pores; and these pores, judging from analogy, probably serve to emit an odour. (66. Stoliczka, ‘Journal of the Asiatic Society of Bengal,’ vol. xxxiv. 1870, p. 166.)

Figure 33: Sitana minor. Male with the gular pouch expanded (from Gunther’s ‘Reptiles of India’)’

The sexes often differ greatly in various external characters. The male of the above-mentioned Anolis is furnished with a crest which runs along the back and tail, and can be erected at pleasure; but of this crest the female does not exhibit a trace. In the Indian Cophotis ceylanica, the female has a dorsal crest, though much less developed than in the male; and so it is, as Dr. Gunther informs me, with the females of many Iguanas, Chameleons, and other lizards. In some species, however, the crest is equally developed in both sexes, as in the Iguana tuberculata. In the genus Sitana, the males alone are furnished with a large throat pouch (Fig. 33), which can be folded up like a fan, and is coloured blue, black, and red; but these splendid colours are exhibited only during the pairing-season. The female does not possess even a rudiment of this appendage. In the Anolis cristatellus, according to Mr. Austen, the throat pouch, which is bright red marbled with yellow, is present in the female, though in a rudimental condition. Again, in certain other lizards, both sexes are equally well provided with throat pouches. Here we see with species belonging to the same group, as in so many previous cases, the same character either confined to the males, or more largely developed in them than in the females, or again equally developed in both sexes. The little lizards of the genus Draco, which glide through the air on their rib-supported parachutes, and which in the beauty of their colours baffle description, are furnished with skinny appendages to the throat “like the wattles of gallinaceous birds.” These become erected when the animal is excited. They occur in both sexes, but are best developed when the male arrives at maturity, at which age the middle appendage is sometimes twice as long as the head. Most of the species likewise have a low crest running along the neck; and this is much more developed in the full-grown males than in the females or young males. (67. All the foregoing statements and quotations, in regard to Cophotis, Sitana and Draco, as well as the following facts in regard to Ceratophora and Chamaeleon, are from Dr. Gunther himself, or from his magnificent work on the ‘Reptiles of British India,’ Ray Soc., 1864, pp. 122, 130, 135.)

A Chinese species is said to live in pairs during the spring; “and if one is caught, the other falls from the tree to the ground, and allows itself to be captured with impunity”–I presume from despair. (68. Mr. Swinhoe, ‘Proc. Zoolog. Soc.’ 1870, p. 240.)

Figure 34: Ceratophora Stoddartii.
Upper figure, male;
lower figure, female.

There are other and much more remarkable differences between the sexes of certain lizards. The male of Ceratophora aspera bears on the extremity of his snout an appendage half as long as the head. It is cylindrical, covered with scales, flexible, and apparently capable of erection: in the female it is quite rudimental. In a second species of the same genus a terminal scale forms a minute horn on the summit of the flexible appendage; and in a third species (C. Stoddartii, fig. 34) the whole appendage is converted into a horn, which is usually of a white colour, but assumes a purplish tint when the animal is excited. In the adult male of this latter species the horn is half an inch in length, but it is of quite minute size in the female and in the young. These appendages, as Dr. Gunther has remarked to me, may be compared with the combs of gallinaceous birds, and apparently serve as ornaments.

Figure 35: Chamaeleo bifurcus.
Upper figure, male;
lower figure, female.

Figure 36: Chamaeleo Owenii.
Upper figure, male;
lower figure, female.

In the genus Chamaeleon we come to the acme of difference between the sexes. The upper part of the skull of the male C. bifurcus (Fig. 35), an inhabitant of Madagascar, is produced into two great, solid, bony projections, covered with scales like the rest of the head; and of this wonderful modification of structure the female exhibits only a rudiment. Again, in Chamaeleo Owenii (Fig. 36), from the West Coast of Africa, the male bears on his snout and forehead three curious horns, of which the female has not a trace. These horns consist of an excrescence of bone covered with a smooth sheath, forming part of the general integuments of the body, so that they are identical in structure with those of a bull, goat, or other sheath-horned ruminant. Although the three horns differ so much in appearance from the two great prolongations of the skull in C. bifurcus, we can hardly doubt that they serve the same general purpose in the economy of these two animals. The first conjecture, which will occur to every one, is that they are used by the males for fighting together; and as these animals are very quarrelsome (69. Dr. Buchholz, ‘Monatsbericht K. Preuss. Akad.’ Jan. 1874, p. 78.), this is probably a correct view. Mr. T.W. Wood also informs me that he once watched two individuals of C. pumilus fighting violently on the branch of a tree; they flung their heads about and tried to bite each other; they then rested for a time and afterwards continued their battle.

With many lizards the sexes differ slightly in colour, the tints and stripes of the males being brighter and more distinctly defined than in the females. This, for instance, is the case with the above Cophotis and with the Acanthodactylus capensis of S. Africa. In a Cordylus of the latter country, the male is either much redder or greener than the female. In the Indian Calotes nigrilabris there is a still greater difference; the lips also of the male are black, whilst those of the female are green. In our common little viviparous lizard (Zootoca vivipara) “the under side of the body and base of the tail in the male are bright orange, spotted with black; in the female these parts are pale-greyish-green without spots.” (70. Bell, ‘History of British Reptiles,’ 2nd ed., 1849, p. 40.) We have seen that the males alone of Sitana possess a throat-pouch; and this is splendidly tinted with blue, black, and red. In the Proctotretus tenuis of Chile the male alone is marked with spots of blue, green, and coppery-red. (71. For Proctotretus, see ‘Zoology of the Voyage of the “Beagle”; Reptiles,’ by Mr. Bell, p. 8. For the Lizards of S. Africa, see ‘Zoology of S. Africa: Reptiles,’ by Sir Andrew Smith, pl. 25 and 39. For the Indian Calotes, see ‘Reptiles of British India,’ by Dr. Gunther, p. 143.) In many cases the males retain the same colours throughout the year, but in others they become much brighter during the breeding-season; I may give as an additional instance the Calotes maria, which at this season has a bright red head, the rest of the body being green. (72. Gunther in ‘Proceedings, Zoological Society,’ 1870, p. 778, with a coloured figure.)

Both sexes of many species are beautifully coloured exactly alike; and there is no reason to suppose that such colours are protective. No doubt with the bright green kinds which live in the midst of vegetation, this colour serves to conceal them; and in N. Patagonia I saw a lizard (Proctotretus multimaculatus) which, when frightened, flattened its body, closed its eyes, and then from its mottled tints was hardly distinguishable from the surrounding sand. But the bright colours with which so many lizards are ornamented, as well as their various curious appendages, were probably acquired by the males as an attraction, and then transmitted either to their male offspring alone, or to both sexes. Sexual selection, indeed, seems to have played almost as important a part with reptiles as with birds; and the less conspicuous colours of the females in comparison with the males cannot be accounted for, as Mr. Wallace believes to be the case with birds, by the greater exposure of the females to danger during incubation.