The love-fights of swallows, linnets and kingfishers, and the curious aerial evolution of the swift are similar manifestations of vigour and delight in movement[64] as a sexual excitant to pairing. Some male doves have a remarkable habit of driving the hen for a few days before she lays the eggs. On these occasions his whole time is spent in keeping her on the move, and he never allows her to settle or rest for a minute except on the nest.[65]
This last case affords a striking illustration of the real object of all these elaborate movements. The male albatross, an ugly and dull-coloured bird,[66] during courtship stands by the female on the nest, raises his wings, spreads his tail, throws up his head with the bill in the air, or stretches it straight out or forwards as far as he can, and then utters a curious cry.[67] But the most interesting example that I have been able to find recorded of dancing among birds is the habit of waltzing, common to the male, and in a lesser degree to the female ostrich. It is thus described by S. Cronwright Schreiner.[68]
"After running a few yards they (the ostriches) will stop, and with raised wings spin round rapidly for some time until quite giddy, when a broken leg occasionally occurs.... Vigorous cocks 'roll' when challenging to fight or when wooing a hen. The cock will suddenly bump down on his knees (ankle joints), open his wings, and then swing them alternately backwards and forwards as if on a pivot. At such a time the bird sees very imperfectly, if at all, in fact he seems so preoccupied that if pursued one may often approach unnoticed. Just before 'rolling,' a cock, especially if courting a hen, will often run slowly and daintily on the points of his toes, with neck slightly inflated, upright and erect, the tail half dropped and all his body feathers fluffed up; the wings raised and expanded, the inside edges touching the sides of the neck for nearly the whole length, and the plumes showing separately like an open fan. In no other attitude is the splendid beauty of his plumage displayed to such advantage."
In this case it is very suggestive to find that it is the male ostrich who takes upon himself the task of hatching and rearing the young. Perhaps this accounts for the female ostrich being able to dance as well as the male. There are very few examples of birds who are bad fathers. Often the male rivals the female in love for the young; he is in constant attendance in the vicinity of the nest; he guards, feeds and sings to the female, and sometimes shares with her the duty of incubation. This is done by the male wood-pigeon, missel-thrush, blue martin, the buzzard, stone-curlew, curlew, dottrel, the sandpiper, common gull, black-coated gull, kittiwake, razorbill, puffin, storm-petrel, the great blue heron and the black vulture. Among these birds it is usual for the family duties to be performed quite irrespective of sex, and the parent who is free takes the task of feeding the one who is occupied. As soon as one family is reared many birds at once burden themselves with another. Audubon records the case of the blue bird of America, who works so zealously that two or three broods are reared at the same time, the female sitting on one clutch, while the male feeds the young of the preceding brood.[69]
Next in importance to dancing and movement in the aid of courtship among birds is their use of song and display of decorative plumage. With them it would seem, even more than among the mammals or with man, sexual desire raises and intensifies all the faculties, and lifts the individual above the normal level of life. The act of singing is a pleasurable one, an expression of superabundant energy and joyous excitement. Thus love-songs, serving first probably as a call of recognition from the male to the female, came to be used as a means of seduction. Every one is familiar with the exquisite lyrical tournaments of our nightingales; their songs during the love season do not cease by day or by night, so that one wonders when sleep can be taken; but as soon as the young are hatched the music ceases, and harsh croaks are the only sound left.[70] The song of the skylark, with its splendid note of freedom, is more melodious and more frequent in the season of love's delirium.[71] Another bird, the male of the weaver bird, builds an abode of pleasure for himself, wherein he retires to sing to his mate.[72] A very beautiful case of the use of these love-calls by the tyrant bird (Pitangus Bolivianus) is recorded by W.H. Hudson.[73]
"Though the male and female are greatly attached they do not go afield to hunt in company, but separate to meet at intervals during the day. One of the couple (say the female) returns to the trees where they are accustomed to meet, and after a time becoming impatient or anxious at the delay of her consort, utters a very long, clear call-note. He is perhaps a quarter of a mile away, watching for a frog beside a pool, or beating over a thistle bed, but he hears the note and presently responds with one of equal power. Then, perhaps, for half-an-hour, at intervals of half-a-minute, the birds answer each other, though the powerful call of the one must interfere with his hunting. At length he returns: then the two birds, perched close together, with their yellow bosoms almost touching, crests elevated, and beating the branch with their wings scream their loudest notes in concert—a confused, jubilant noise that rings through the whole plantation. Their joy at meeting is patent, and their action corresponds to the warm embrace of a loving human couple."
Some birds, who are ill-endowed from a musical point of view, have their wing feathers or tails peculiarly developed and stiffened, and are able to produce with them a strange snapping or cracking sound. Thus several species of snipe make drumming or "bleating" noises—something like the bleat of a goat—with their narrowed tails as they descend in flight.[74] Magpies have a still more curious method of call, by rapping on dry and sonorous branches, which they use not only to attract the female, but also to charm her. We may say that these birds perform instrumental music.[75]
The exercise of vocal power among birds seems to be complementary to the development of accessory plumes and ornaments. All our finest singing birds are plainly coloured, with no crests, neck or tail plumes to display. The gorgeously ornamented birds of the tropics have no song, and those which expend much energy in display of plumage, as the turkey and peacocks, have comparatively an insignificant development of voice.[76] The extraordinary manner in which birds display their plumage at the time of courting is well known. Let us take one example—the courtship of the Argus pheasant. This bird is noted for the extreme beauty of the male's plumage. Its courtship has been beautifully observed by H.O. Forbes—[77]
"It is the habit of this bird to make a large circus, some ten or twelve feet in diameter, in the forest, which it clears of every leaf and twig and branch, till the ground is perfectly swept and garnished. On the margin of this circus there is invariably a projecting branch or high arched rest, at a few feet elevation from the ground on which the female bird takes its place, while in the ring the male—the male bird alone possesses great decoration—shows off all its magnificence for the gratification and pleasure of his consort, and to exalt himself in her eyes."
In this picture we have all the characteristic features of the display of personal beauty in which many birds delight. Any one may see such performances for themselves. The male chaffinch, for instance, will place himself in front of the female that she may admire at her ease his red throat and blue head; the bullfinch swells out his breast to display the crimson feathers, twisting his black tail from side to side; the goldfinch sways his body, and quickly turns his slightly expanded wings first to one side, then to the other, with a golden flashing effect.[78] Even birds of less ornamental plumage are accustomed to strut and show themselves off before the females. Birds often assemble in large numbers to compete in beauty before pairing. The Tetras cuspido of Florida and the little grouse of Germany and Scandinavia do this. The latter have daily amorous assemblies, or cours d'amour, of great length, which are renewed every year in the month of May.[79] It seems certain that this æsthetic display is conscious and pre-meditated; for while most pheasants parade before their females, two of the species—the Crossoptilon auritum and the Phasianus Wallichii—which are of dull colour, refrain from doing so, being apparently conscious of their modest livery.[80]