The Courtship of Animals

by W. P. Pycraft

We cannot credit these birds with notions on the importance of the regular discharge of the evacuations. Equally mysterious is the development of the envelope enclosing the fæcal matter. This is jelly-like in substance, and of considerable thickness, and is enclosed within a very delicate skin or pellicle, enabling one to lift the whole in the fingers without soiling them. How and where it is formed should not long evade discovery. But how it has come to be is another matter. We can, at any rate, vaguely account for responses of the organism to internal stimuli reacting directly on the individual, but here is an elaborate mechanism evolved in response to extra-personal needs: and which cannot be regarded as of exactly the same configuration as the instinct to feed the young.

A return must be made to the nature of the early phases in the procession of the reproductive instincts. Mr. Howard’s study of the Warblers seems to show conclusively that these first manifest themselves in an overmastering desire to seize upon territory large enough to ensure an abundance of food for the offspring that are yet to be. To this end the males arrive from their far-distant winter quarters at least a week in advance of the females. Since each returns approximately to the scene of last year’s nursery, the arrivals are fairly distributed at the first; but nevertheless this distribution inevitably brings a conflict of interests between one or more males, perchance young birds about to start in life, and having therefore no definite objective. But whatever the reason, the competition is there. The strongest male remains in possession, and immediately commences to express the ecstasy of feeling which possesses him in continuous outbursts of song. Such, doubtless, answer to the bellowing of the male stag. They advertise the presence of a male to the female, who, as she arrives, would seem to be already stirred by the rising storm of sexual desire, for having once discovered a male in possession of the all-necessary site for the nest, and the equally necessary domain, each settles down to conjugal bliss: within twenty-four hours the task of building has begun. There is evidently here no sexual selection in Darwin’s sense: no choice from among a number of males of the individual which most excites desire within her; but the mating of the most mettlesome, most virile males has been determined before her arrival and by a double sieve. In the first place, the duller-witted birds fail to secure suitable territory, and in the second, the territory, having been taken, must be held by force, so that only the strongest males remain to mate when the females eventually arrive. So far as one can see, selection is less exacting in the case of the females, which apparently need do little more than respond to the advances of the males.

Plate 22.

From a drawing by H. Grönvold.

FIGHTING FOR TERRITORY.

Two Black-caps are here seen fighting for their annual breeding territory. A Chiff-chaff has been unable to resist the excitement of conflict.

Face page 140.

With the advent of the females the amorous instincts of the male speedily gather force; but for their satisfaction it is imperative that the female should be possessed by a like desire. To provoke this, for it is essential to the well-being of the race that offspring should be produced as early as possible, some form of aphrodisiac seems to be necessary. This fact has never been properly realized, though it is implied in Darwin’s theory of “Sexual Selection.” Here, however, it was used to account for the evolution of resplendent coloration, eccentric postures, and dances which, it was assumed, enabled or induced the female to choose the most mettlesome males. What obtained among sombre-clad species, appears to have excited no curiosity among the students of the evolution theory. Hence it comes somewhat as a surprise to find that the soberly-clad Warblers behave exactly as though they too wore coats of many colours. After what has been said in the last chapter on this head it will be unnecessary to describe these displays among the Warblers in detail, more especially as my friend Mr. Howard has kindly allowed me to use some of the illustrations from his book. These show convincingly enough that the wings and tail are made to play the same part as though they bore all the hues of the rainbow. To bring this fact home compare the figures of some of these small birds clad in sober russet and black with that of the Sun Bittern (Eurypyga helias) in like mood, whose wings and tail when spread, and only then, display bands of vivid chestnut-red, contrasting with bands of black, on a background of grey and buff, variegated with delicate mottlings and vermiculations of black and brown, and streaks of white. In the case of the Warblers, it is to be remarked, the male, in these ecstatic moods, will commonly hold a leaf, or a piece of stick, in his beak, as if suggesting the work of nest-building and its delightful sequence. This, or its equivalent, is a common phase, for the Great Crested Grebe, for example, in these paroxysms will dive and bring up weed, the nest material of the species, as an offering to his mate, or as a stimulant to her yet slumbering passion.

It seems clear, then, that the evolution of colour is not the stimulant to display, for this is present where conspicuous colours are wanting. Yet it can readily be understood how the association of ideas in regard to colour and display arose, for there are cases where this interpretation seems inevitable. Such are afforded by certain sea-birds like the Kittiwake, Guillemot, Fulmar and Cormorant, wherein the inside of the mouth is of a lurid orange-red in the case of the first-mentioned, and of flaming gamboge yellow in that of the others. During moments of sexual ecstasy the mouth is widely opened, as if to charm the beholder with its gaudy hue. Both sexes have the same colouring, and both behave alike. But it is doubtful whether either is conscious that its own mouth is like that exposed to its gaze: the action is sympathetic. No doubt it may play its part in stimulating desire, but we cannot contend from this that it has been evolved by sexual selection, that is to say, that the hues have undergone a process of gradual intensification owing to the deliberate rejection of the less gaily-coloured suitors. The tendency to develop colour in the mouth would appear to be latent in all birds.