MOUTHS WITH MEANINGS
The young kittiwake differs in appearance from the parent birds in a
quite uncommon manner, for, being prettily and saliently marked, it looks
like a mature gull of another species, whereas the young of other gulls,
being plain brown things, suggest their juvenility on the analogy of
pheasants or birds of paradise. The general colour is mauvy grey, but
black, falling here and there upon it, seems striving to blot it out.
Half of the wings are thus darkened, and a broad half-moon of sooty black
nearly encircles the neck, looking like black velvet on the back of it,
where it is by much the broadest. There is a clouded black mark, too, on
either side of the head, with some nuances of black between, black tips
the tail, and the beak is all black. The _tout ensemble_ of all this is
very pretty, and the young kittiwake is a pretty bird. Mauve and black
velvet is the dress it comes out in, and it looks like a soft little
dove. Many might admire it beyond the grown bird, but, personally, I
prefer the latter.
One of these well-grown young kittiwakes has just been fed by the mother,
or father--but call it the mother, it always sounds better. Being
importuned by sundry little peckings at her beak, she opened it, and the
young one, thrusting in its own, helped himself as though her throat
were a platter. It was much the same as with the fulmar petrels. Numbers
of the young have left their nests, and keep all together, standing on
the rocks or floating on the sea. Others remain, and I notice that these
keep flapping their wings. This must strengthen them, and have the effect
of preparing Dædalus for his first flight--for it seems probable that
these particular ones have not made it. But they have, though, and bang
goes a provisional hypothesis! Every moment, to laugh at me, one or other
of them is flying out from the ledges, whilst others are returning to
them.
When one of these young kittiwakes opens its bill, it is at once
apparent that the inside of its mouth is much less brilliantly coloured
than it is in the parent bird, being of a pale pinkish, merely, with,
perhaps, a tinge of light yellow. As for the grown bird's mouth, one can
hardly exaggerate the lurid brightness of it. The whole buccal cavity,
including, as I think is usual, the tongue, is of a fine rich red, or
orange-red colour, carrying on that of the naked skin adjoining the
mandibles outside, with which, indeed, it is continuous. It is just the
same in the case of the old and young shag. The mouth of the former
presents a uniform surface of splendid gamboge, whilst that of the latter
is almost the natural pink, only just beginning to pass into yellow. In
the young guillemot, also, the interior of the mouth is pinkish merely,
whilst in the grown bird it is of a pleasing lemon or gamboge. With the
fulmar petrel again, we have much the same thing, though here--and
this is significant--the difference, as well as the actual colour, is
less striking. These varying degrees of brilliancy of colouring in this
particular region, as between the mature and immature form, must surely
have some meaning, and as it goes hand-in-hand with a similar, if not,
as I believe, an identical difference in the hue of the naked facial
integument, as well as with the pattern and shade of the plumage, I feel
persuaded that all three are governed by the same general law.
As explained by Darwin--and nothing better, that I can see, than
opposition has ever been opposed to his views--the beauty of certain
birds has been acquired through the principle of sexual selection, and
the lesser degree of it, which we notice in the young, represents the
earlier and less-finished beauty of the adult in times gone by. Of all
the elements which go to make up the beauty thus acquired, colour, on
the whole, plays the most conspicuous part, and nothing can be more
brilliant and striking than some of the colours that I am here speaking
of. The only reason, therefore, why, in their use, and the laws that have
governed their acquirement, they should be thought to differ from the
hues and tintings of the plumage, or of the naked outer skin--the cere
or the labial region--would be their habitual, necessary concealment.
If, then, it can be shown that, far from their being always concealed,
they are prominently displayed during the breeding season by certain
birds which possess them in a marked degree, then, as far as these
birds are concerned, there ceases to be a reason for thus, in idea,
separating them. Let us see, now, how far this is the case. To begin with
these kittiwakes, in their courting, or rather connubial actions on the
ledges--as may be seen now, but much more earlier in the year--both sexes
open their bills widely, and crane about, with their heads turned toward
each other, whilst at the same time uttering their shrieking, clamorous
cry. The motion, however, is often continued after the cry has ceased,
and this we might expect if the birds took any pleasure in the brilliant
gleam of colour which each presents to, and, as it were, flashes about
in front of the other. The effect of this it is not easy to exaggerate,
and if it is extremely noticeable to an onlooker at some little distance,
what must it be to the bird itself, who looks right into the almost
scarlet cavity? We have only to think of the inside of some shells, or of
a large, highly-coloured flower-cup, to understand the kind of æsthetic
pleasure that may be derived from such a sight.
Similar, but much more striking, is the nuptial behaviour of the fulmar
petrel. A pair of these birds lying near together, on some ledge or
cranny of the rock, will, every few minutes, open their bills to the
very widest extent, at the same time blowing and swelling out the skin
of the throat, including that which lies between the two sides of the
lower mandible, until it has a very inflated appearance. In this state
they stretch their heads towards each other, and then, with languishing
gestures and expression, keep moving them about from side to side,
uttering whilst they do so, but by no means always, a hoarse, unlovely
sort of note, like a series of hoarse coughs or grunts, as though in
anger--and indeed, it is uttered in anger, too. But though these motions,
with the distension of the jaws, always, as far as I have seen, accompany
the note when it is uttered, yet they are often continued afterwards, and
sometimes commence and end in silence, so that one has to conclude that
they are themselves of importance, and may have as much, or even more, to
do with the expression of the bird's feelings as the vocal utterance has.
It is difficult to give an adequate idea of the strange, lackadaisical
appearance which these birds present while acting in the above-described
manner. With widely-gaping bills, swelled throats, necks stretched out,
and heads moving slowly all about, now up, now down, now to this side,
now to that, they look sometimes "sick of love," like Solomon, and
sometimes as though about to be sick indeed--in fact, on the point of
vomiting. All the bird's actions are peculiar, but none more so than
this wide gaping distension of the mandibles, with the full view that it
offers of the whole interior cavity of the mouth. This last is not indeed
brilliant, as is that of the kittiwake, but, for all that, it is very
pleasing, of a delicate mauvy blue, æsthetic in its appearance, and in
harmony with the soft and delicate tinting of the plumage. There is no
reason to suppose that the latter beauty is unappreciated by the bird
itself, when seen in the opposite sex. Why, then, should the pale mauve
or blue of the inside of the mouth--this purple chamber flung open for
inspection during the season of courtship or of nuptial dalliance--be not
appreciated too?
The razorbill's mouth, inside, is of a conspicuous light yellow, which,
when exposed suddenly to view, contrasts very forcibly with the black
of the beak and upper plumage. In dalliance these birds throw the
head straight up into the air, and, opening their clean-cut bills, so
that one sees the gay interior like a line of bright gamboge, utter
a deep guttural note, which is prolonged and has a vibratory roll in
it, like the cry of the gorilla when angry--_si parva licet componere
magnis_--as described by Du Chaillu. It is not loud, however, and so is
easily lost amidst elemental sounds and the cries of other birds. The
vibratory character of the note becomes more marked under the influence
of excitement, and the mandibles themselves vibrate as they are opened
at intervals, somewhat widely. In the midst of their duet the pair toss
their heads about, catch hold of each other's beaks, and give quick
little emotional nibbles at the feathers of their throats or breasts. If
we can suppose that the birds are interested in each other's appearance
whilst thus acting--that they admire or are sexually excited by one
another--then it would be strange if the bright flashing yellow so
constantly exhibited did not play its full part in producing this result.
Imagine ourselves razor-bills, and thus acting. Could we be blind to
such revelations? I think not.
The pretty little black guillemot--the dabchick of ocean--may often be
seen sitting in a niche of the cliffs, and calling to another--its mate
presumably--either above or below it. The cry is, for the most part,
a weak, twittering sound, but occasionally rises into a very feeble
little wail or scream. All the while the bird is uttering it he keeps
raising and again depressing his head and opening his beak so as to
show conspicuously the inside of his mouth, which is of a very pretty
rose or blush-red hue, almost as vivid as that of the feet. The beak is
opened more widely than would seem to be necessary for the production of
the sound, as if to show this coloration, even though, for the moment,
there may be no other bird there to see it. If, however, the rosy inward
complexion were in any way an attraction, it would be natural for a bird,
wanting its mate, to associate the wish with the action of opening the
beak, just as a lonely dove in a cage will coo and bow as to a partner.
As a matter of fact, the crying bird very soon flies to the other one
(or _vice versâ_), and, standing beside her, utters his little twitter
as a greeting. She, being couched down, responds by raising her head,
so that the tip of her beak touches, or nearly touches, his. Then he
couches also, and sitting thus, side by side--comfy on the sheer edge of
the precipice--the two turn, from time to time, their heads towards each
other, open their bills, and twitter together. Every time they open them
the pretty rose tapestry of the mouth-chamber must be plain to each or
either, and the more so that they are _vis-a-vis_.
In all these four birds, therefore, we have a nuptial habit of distending
the jaws, side by side with a brilliant or pleasing coloration of the
region which, by such action, is exhibited. Moreover, in the case of
one of them, more particularly--viz. the fulmar petrel--this distension
may be unaccompanied with any note, though it always is with the odd
gestures and lackadaisical expression which I have tried to describe.
In other words, the beak is sometimes opened as a part of the bird's
nuptial actions, and not merely with a view to the production of sound.
That originally this alone would have been the motive of its being so
can hardly, I suppose, be doubted, but may it not be possible that the
eye has gradually come to share in a pleasure which was, at first,
communicated through the ear alone, and that a process of selection,
founded, perhaps, on some initial freshness of colouring, has in time
produced a special kind of adornment? If this were so, we might expect
that some of the birds so adorned would have the habit of opening the
bill in this manner without uttering any note at all, or, at least,
that they would very frequently do so. Such an instance we have in the
shag, that smaller and more adorned variety of the cormorant, which is
much more common on our northern coasts than the so-called common one.
One of the most ordinary nuptial actions of these birds is to throw
the head into the air, and open and shut the beak several times in
succession; and sometimes they hold it wide open for several seconds
together. Each time, as the jaws gape, a splendid surface of bright
gamboge yellow is exhibited, which the human eye, at any rate, has to
admire, and which exactly matches with the naked yellow skin at the base
of the two mandibles on either side, where they become lost in what may
be called the bird's cheek. This exterior brightly-tinted surface is
continuous with the interior and much larger one, and my view is that the
colour of the latter represents an extension of that of the former, by
a similar process of sexual selection. There is no doubt whatever that
this outward adornment largely adds to the handsome appearance of the
shag, and probably those naturalists who believe in sexual selection at
all will think it as much due to that agency as the crest and the sheeny
green plumage. But if the closely similar colouring of the adjacent
interior region is to be looked on as merely fortuitous (we escape here,
thank heaven, from the all-pervading protective theory), why should the
other be thought to be anything more? If the shag had not this habit
of opening its mouth and thus displaying what is, in itself, so very
striking, it would be difficult, I think, to accept sexual selection as
an explanation even of the facial adornment, since, if the one effect
were nonsignificant, so might the other be. As it is, I can see no reason
why it should not have brought about both.
I have often watched shags thus throwing up their heads and opening and
shutting their jaws at one another, and though I have generally been
fairly close to them I have never heard them utter a note whilst so
doing. I consider these actions--together with other still more peculiar
ones, which they indulge in during the breeding season--to be of a sexual
character, and, if so, this silent and oft-repeated distension of the
jaws must have some kind of meaning. The large and brilliantly-coloured
surface which is thus displayed supplies this meaning, as I am inclined
to think.
The fact that some birds--I have not the knowledge to say how many--which
do not open the beak in this way, have yet the inside of the mouth
brightly or conspicuously coloured, may seem to throw doubt on the theory
here advanced; but of course sexual selection is not the only power which
may have produced such coloration, and the likelihood of its having done
so is decreased if there is no outer facial adornment to match that
within. The cuckoo is one such example, for--I speak on the strength of
young ones which I have seen in the nest--the whole of its inner mouth
is of a really splendid salmon colour. When approached, the nestling
cuckoo assumes a most threatening attitude, alternately dilating and
drawing itself in, now receding into the nest, now rising up in it as
though to strike, having all the while its mouth wide open and hissing
violently. Its feathers are ruffled, and altogether it has a quite
terrifying aspect, to which the triangular flaming patch that seems to
burst out of the centre of it--for the head is drawn right back upon the
body--very largely contributes. Especially is this so when, as is mostly
the case, there is considerable shadow in the recess of the nest, amidst
the surrounding foliage. If it can be supposed that the large false head
and painted eyes of the puss or elephant hawk-moth caterpillars have
been acquired as a protection against enemies--as to which see Professor
Poulton's interesting suggestion[6]--then it certainly seems to me more
than possible that the flame-like throat of the young cuckoo has been
developed in the same manner, _pari passu_ with the loud, snake-like
hiss and intimidating gestures. In conclusion, I would suggest that the
bright or pleasingly-coloured mouth-cavity which some birds possess may
have a distinct meaning, and be the product either of natural or sexual
selection.
[Footnote 6: _The Colours of Animals_ (International Scientific
Series).]
[Illustration: AERIAL PIRACY]