A great step in advance is taken when we come to study the courtship and sexual relationships of birds and mammals. There are many examples, in particular among birds, of a beautiful and high standard of love-morality. To the physical fondness of the sexes for one another there is now added a wealth of what must be recognised as psychical attraction, which finds its expression in many diverse ways. We shall find all forms of sexual association, very similar to marriage in the human species. There are temporary unions formed for the purpose of procreation, after which the partners separate and cease to care for one another. Polygamy is frequent, polyandry also occurs, and there are many cases of absolute profligate promiscuity. We shall, indeed, find the suggestion of all the sexual sins of humanity, every form of coquetry, of love-battles, jealousy and the like. There are as well many examples of monogamic unions lasting for the lives of the partners. This is especially the case with birds. Among the higher mammals polygamy is most common, but permanent unions are formed, especially among the anthropoid apes. Thus strictly monogamous marriages are frequent among gorillas and orang-utans, the young sometimes remaining with their parents to the age of six years, while any approach to loose behaviour on the part of the wife is severely punished by the husband.[50] We find both the matriarchate and patriarchate family; and we may observe the greatest difference in the conduct of the parents in their care of offspring. Even a rapid examination of these customs is worth while, for they cast forward many suggestions on our sexual, domestic, and social relationships.
Let us take first the phenomena of courtship.
It is possible to give only the briefest outline of this fascinating subject. We will begin with the law-of-battle. Courtship without combat is rare among mammals; it is less common in many species of birds. Special offensive and defensive weapons for use in these love-fights are found; such are the larger canine teeth of many male mammals, the antlers of stags, the tusks of elephants, the horns of antelopes, goats, oxen and other animals, while among birds the spurs of the cock and allied species are examples of sexual weapons.[51]
"The season of love is the season of battle," says Darwin. To those who understand love there will be no cause of surprise in these procreative explosions. There can be no doubt that such combats are a stimulus to mutual sexual excitement in the males who take part in them and the female who watches them. Throughout Nature love only reaches its goal after tremendous expenditure of energy. Courtship is the prelude to love. The question is—what form it shall take? It is this that even yet we have not decided. But the importance of courtship cannot be overlooked. We must regard it as the servant of the Life-force. In the fine saying of Professor Lloyd Morgan,[52] "the purpose of courtship reveals itself as the strong and steady bending of the bow, that the arrow may find its mark in a biological end of the highest importance in the survival of a healthy and vigorous race."
Even the most timid animals will fight desperately under the stimulus of sex-passion. Hares and moles battle to the death in some cases; squirrels and beavers wound each other severely. Seals grapple with tooth and claw; bulls, deer and stallions have violent encounters, and goats use their curved horns with deadly effect.[53] The elephant, pacific by nature, assumes a terrible fury in the rutting season. Thus, the Sanskrit poems frequently use the simile of the elephant goaded by love to express the highest degree of strength, nobility, grandeur and even beauty.[54] It is hardly necessary to point out that in these love-conflicts we may find the sources of our own brute passions of jealousy, and the origin of duels, murders and all the violent crimes committed by men under the excitement of sexual emotion—the tares among the wheat of love that drive men mad and wild.
In birds it is among the gallinaceæ that love incites the male with warlike fury. The barn-door cock is the type of the jealous male—amorous, vain and courageous.[55] It must be noted that wheresoever supremacy in love is obtained by force the male has necessarily become, through the action of selection, stronger and better armed than the female. Among birds, where the law of battle largely gives place to a gentler wooing, there are many species in which the female is larger and stronger than the male, and a much greater number where there is no appreciable difference between the sexes. These prove what we have already established among the invertebrates, that there is no necessary correlation between weakness and the female sex. But to this question, so important in its bearing on the relative position of the sexes, I shall return later.
The acquisition of mates does not depend entirely upon strength and victory in battle. Many male mammals have crests and tufts of hair, and other marks of beauty, such as bright colouring, are often conspicuous. These are used to attract the females. The incense of odoriferous glands, which become specially functional during the breeding season, are another frequent means of sexual attraction.[56] Even many of the amatory duels are not really fights between rivals. They are rather parades, or tournaments, used by the males as a means of displaying their beauty and valour to the females. This is frequent among the contests of birds, as, for instance, the grouse of Florida (Tetras cuspido), which are said to assemble at night to fight until morning with measured grace, and then to separate, having first exchanged formal courtesies.[57]
It is among birds that the notes of joy in love break out with a wonderful fascination. They are the most perfect of lovers; strength is often quite set aside, and the eye and ear of the mate alone is appealed to. The males (and also, in some cases, the females) use many æsthetic appeals to stimulate passion, such as dancing, beauty of plumage, and the art of showing it, as well as sweetness of song and diverse love-calls. There are numerous examples of affectionate partnerships between the sexes, in some cases lasting for life. The female Illinois parrot, for instance, rarely survives the death of her mate. Similarly the death of either sex of the panurus is said to be fatal to its companion. The affection of these birds is strong; they always perch side by side, and when they fall asleep one of them, usually the male, covers the other with its wing. The couples of the golden woodpeckers and doves live in perfect unison. Brehm records the case of a male woodpecker who, after the death of his mate, tapped day and night with his beak to recall the absent one, and when at last discouraged, he became silent and never recovered his gaiety.[58] According to some estimates monogamy prevails among ninety per cent of birds.[59] This is explained by the steady co-operation of both sexes in forming the home and caring for the young, for it is surely the working together which causes their love to outlast the excitement of the procreative season. Sometimes we find this affection flowing out into a wider altruism, extending beyond the family to the social group; which again is surely at once the condition and result of these beautiful and practical love-partnerships.
Those who have read the absorbing pages of Darwin devoted to the consideration of the sexual characters of birds, or know the examples given by Büchner, Audubon, Epinas, Wallace and other naturalists, or, better still, those who have watched and noted for themselves the love-habits of birds, will find it impossible to withhold admiration for the poetic character of many of these courtships and marriages, which put too often our own human matings to utter shame.
Let us look first at the love-dances. Dancing as a means of attracting the right pitch of passion in the male and the female has always been used in the service of the sexual instinct. It gives the highest and most complex expression of movement, and may be said to have been evolved by love from the more brutal courtships of battle display.[60] The characteristic features of the amatory dances of birds are well known; they may be witnessed frequently during the pairing season. The male blackbird, for instance, is full of action as he woos his mate; he flirts his tail, spreads his glossy wings, hops and turns; chases the hen, and all the time chuckles with delight. Similar antics are performed by the whitethroat. The male redwing, again, struts about before his female, sweeping the ground with his tail, and acting the dandy.[61] The crested duck raises his head gracefully, straightens his silky aigrette, struts and bows to his female, while his throat swells and he utters a sort of guttural note.[62] The common shield duck, geese, wood-pigeons, carrion-vultures, and many other birds have been observed to dance, spread their tails, chase one another, and perform many strange courting parades. A careful observer of birds, Mr. E. Selous, who is quoted by Havelock Ellis,[63] has found that all bird dances are not nuptial, but that some birds—the stone-curlew (or great plover), for example—have different kinds of dancing. The nuptial dances are taken part in by both the male and female, and are immediately followed by conjugation; but there are as well other dances or antics of a non-sexual character, which may be regarded as social, and these too are indulged in by both sexes.