The Courtship of Animals

by W. P. Pycraft

Plate 26.

Photo copyright by D. Seth-Smith.

ANOTHER ASPECT OF THE KAGU’S “DISPLAY.”

Herein two birds are seen facing one another with the great head-crest fully erected. While in this mood these birds will strut up and down with mincing gait and drooping wings. This is a posture commonly assumed during momentary excitement, whereas the posture shown in plate 24 is apparently only assumed during moments of sexual excitement.

[Face page 154.

Instances of such impotency on the part of either sex are wanting, and we can only speculate as to how such cases would be met. Would a female who had chanced to settle in the territory of a male whose sexual impulses carried him no further than seizing territory remain with him throughout the mating season, held by an imperfectly roused, ill-defined, sexual instinct? Or, eventually becoming mate-hungry, and failing to stimulate him to perform his part, would she desert him and seek another mate? On the other hand, would a male, failing to arouse response in the female he had secured, drive her away and supplant her?

In other words, are we then justified in postulating differential effects in regard to display: a minimum of intensity to ensure mating? A display of some sort is essential. It may be feeble as compared with that of another species—that of the Sparrow, for instance, compared with that of the Peacock—but it must be sufficiently good of its kind to effect its purpose, which is to “hustle” up the production of offspring. A phlegmatic but virile male, or a too feeble performer, is almost as certainly doomed to extinction as an impotent male; for his offspring will probably be eliminated by the adverse conditions of existence to which their late appearance exposed them. Where a female settles down with a male which does not attain to the standard of display characteristic of his race, it is conceivable she may sooner or later seek a mate elsewhere, deserting the phlegmatic bird as if under the impression that she had made the mistake of settling down with one of her own sex. There is no need that the female should have to “select” the best performer of a number of males displaying at the same time and place as a number of rivals.

Finally, the ornamental crests and frills, and the vivid hues which so many birds display have not arisen, as is generally supposed, as a direct result of the selection, by the females, of the most vividly coloured, or ornamented, from among a number of suitors presenting varying degrees of intensity in ornamentation. Such “frills and furbelows” are to be regarded as “expression points” of internal variations in the germ-plasm, which have been free to develop along their own lines because they have not proved in disharmony with the conditions of the birds’ environment. Their development is to be traced to the stimulating action of the “hormones” which control both pigmentation and structure, as is shown by the fact that both are modified by any interference with the glands in question. Such ornamental features then are the concomitants not the results of Sexual selection.

The development of ornament, whether of colour or structure, may be taken then as an index of specialization, and as one of the many manifestations of that variation which is going on in every part of every living organism.