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 surpassing 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 _blasé_ 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 minivet (_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.