THE PARADISE FLYCATCHER
The cock paradise flycatcher (Terpsiphone paradisi), when in full adult plumage, is a bird of startling beauty. I shall never forget the first occasion upon which I saw him. It was in the Himalayas when night was falling that I caught sight of some white, diaphanous-looking creature flitting about among the trees. In the dim twilight it looked ghostly in its beauty.
It is the two elongated, middle tail feathers which render the bird so striking. They look like white satin streamers and are responsible for the bird's many popular names, such as cotton - thief, ribbon - bird, rocket-bird. But this flycatcher has more than striking beauty to commend it to the naturalist; it is of sur¬passing interest from the point of view of biological theory. The cock is one of the few birds that undergo metamorphosis during adult life, and the species furnishes an excellent example of sexual dimorphism.
Since the day, some years back, when I first set eyes upon the bird; I determined to learn something of its habits; but I had to wait long before I was able to carry out my determination. It was not until I came to Lahore that I saw much of the species. Here let me say 'that the capital of the Punjab, unpromising as it looks at first sight, is, when one gets to know it, a veritable gold mine for the ornithologist.
Paradise flycatchers migrate there in great numbers in order to breed. They arrive at the end of April and at once commence nesting operations. Before describing these, let me, in order to enable non-ornithological readers to appreciate what follows, say a few words regarding the plumage of the bird. The young of both sexes are chestnut in colour, with the exception of a black head and crest and whitish under parts. This plumage is retained by the hen throughout life. After the autumn moult of the second year the two median tail feathers of the cock grow to a length of sixteen inches, that is to say, four times the length of the other tail feathers, and are retained till the following May or June, when they are cast. After the third autumn moult they again grow, and the plumage now begins to become gradually white, the wings and tail being the first portions to be affected by the change; thus the cock is for a time partly chestnut and partly white, and it is not until he emerges from the moult of his fourth autumn that all his feathers are white, with, of course, the exception of those of his head and crest. The bird retains this plumage until death. Cock birds breed in either chestnut or white plumage ; this proves that the metamorphosis from chestnut to white takes place after the bird has attained maturity.
In Lahore this species nests in considerable numbers along the well-wooded banks of the Ravi. Since the birds keep to forest country it is not easy to follow their courting operations for any length of time ; the birds engaged in courtship appear for a moment and then are lost to view among the foliage, but the species is certainly monogamous, and I think there can be but little doubt that the hen courts the cock quite as much as he courts her. On 28th April I was out with Mr. G. A. Pinto, and he saw a couple of hens chasing a cock in white plumage. Presently one of the hens drove away the other, then the cock showed off to the triumphant hen, expanding his wings and uttering a sweet little song, like the opening bars of that of the white-browed fantail flycatcher (Rhipidura albifrontata). I myself was not a witness of that incident, the birds not being visible from where I was standing at the time; but on 3rd June I saw a cock bird in chestnut plumage and a hen fighting; before long the birds disengaged themselves and the male flew off; then a cock in white plumage came up to the hen and gave her a bit of his mind. After this they both disappeared among the foliage. Presently I saw two hens chasing a chestnut-coloured cock. I do not understand the full significance of these incidents, but they tend to refute Charles Darwin's contention that there is competition among cocks for hens but none among hens for cocks, and to show that the hen takes an active part in courtship. To this I shall return.
It does not seem to be generally known that the cock paradise flycatcher is capable of emitting anything approaching a song. Thus Oates writes in The Fauna of British India of these flycatchers, " their notes are very harsh." This is true of the usual call, which is short, sharp, and harsh, something like the twitter of an angry sparrow. But in addition to this the cock has two tuneful calls. One resembles the commencement of the song of the white-browed fantail flycatcher, and the other is a sweet little warble of about four notes. I have repeatedly been quite close to the cock when thus singing and have seen his throat swell when he sang, so there can be no question as to the notes being his. He thus furnishes one of the many exceptions to the rule that brilliantly plumaged birds have no song.
The nest is a deepish cup, firmly attached to two or more slender branches; it is in shape like an inverted cone with the point prolonged as a stalk. It is composed chiefly of vegetable fibres and fine grass; these being coated outwardly by a thick layer of cobweb and small white cocoons. Let me take this opportunity of remarking that cobweb affords a most important building material to bird masons; it is their cement, and many species, such as sunbirds and flycatchers, use it most unsparingly.
The paradise flycatcher seems to delight to build in exposed situations, hence a great many of their nests come to grief, especially in the Punjab, where, if there be anything in phrenology, the bumps of destructiveness and cruelty must be enormously developed in every small boy.
The nesting habits of the paradise flycatcher have been described in detail in the preceding article. They are of considerable biological importance. I would lay especial stress on the active part in courtship played by the hen, the large share in incubation taken by the cock, and the change in the plumage of the cock bird from chestnut to white in the third year of his existence.
Darwin, as I have already pointed out, devoted much time and energy in trying to prove that there is in most species competition among males for females, and that these latter are in consequence able to exercise a selection. They choose the most brilliant and beautiful of their numerous suitors. Thus we have what he calls sexual selection, or, as I should prefer to call it, feminine selection. On this theory the poor cock exercises no selection; any decrepit old hen is good enough for him! He is all eagerness, while the hen is blase and indifferent. This theory is, I submit, improbable on a priori grounds. It is certainly opposed to human experience, and is, I believe, not borne out by animal behaviour.
I have paid some attention to the subject lately, and am convinced that in most cases the desire of the hen for the cock is as great as the desire of the latter for the hen. It was only this morning that I watched two hen orioles trying to drive each other away, while the cock was in a tree near by.
To repeat what I have already said, the hen courts the cock quite as much as he courts her. When a pair of birds mate they are mutually attracted to one another. That there is such a thing as sexual selection I am convinced, but I do not believe that this selection is confined to the hens. The hen selects the best cock she can get to pair with her, while the cock selects the best hen available.
I speak here of monogamous species; among polygamous ones there must of necessity be considerable competition for hens.
The second point upon which I desire to lay stress is the active part taken by the cock paradise flycatcher in incubation. This, again, is, I believe, nothing very uncommon, even in sexually dimorphic species, for I have myself put a cock minvet (Pericrocotus peregrinus) off the nest. Yet this fact seems to dispose of Wallace's theory that the more sombre hues of the hen are due to her greater need of protection, since she alone is supposed to incubate.
As a matter of fact, a bird sitting on a nest is not, in my opinion, exposed to any special danger, for it seems that birds of prey as a rule only attack flying objects.
Finally, there is the extraordinary metamorphosis undergone by the cock in his fourth year. It is difficult to see how this can have been caused by the preference of the hen for white cock birds, since a great many chestnut ones are observed to breed; the dimorphism must, therefore, have originated late in the life history of the species, and although a hen bird might prefer a white to a chestnut husband, it is difficult to believe that she would prefer a skewbald one, and this skewbald state must have been an ancestral stage if we believe that the transition is due to feminine selection of white birds. I may be asked, " If you decline to believe that the hen has greater need of protection than the cock, how do you account for the phenomena of sexual dimorphism, and if it is not sexual selection which has caused the white plumage of the cock paradise flycatcher to arise, what is it ? "
This article has already attained such a length that even had I complete explanations to offer I could not set them forth in this place. I must content myself with giving what I believe to be the key to the solution of the problem. I think that there is little doubt that what a bird looks for in its mate is, not beauty or brilliance of plumage, but vigour and strength. If beauty is a correlative character to strength, then the hen selects the most beautiful of the cocks willing to mate with her, not because of his beauty, but on account of his strength; likewise the cock. Now there is a very intimate connection between the generative cells and the body cells, and the male element tends to dissipate energy and the female element to conserve it. Thus it is that the general tendency of the cock is to become gaily coloured and to grow plumes and other ornaments, while the tendency of the hen is to remain of comparatively sombre hue.