So, too, it must be considered how lethargic these young terns are before they can fly, and how easily they then let themselves be caught, though able to run quickly. When noticed, or approached closely, they crouch, but though this is probably due to an inherited instinct of self-preservation, they do not appear to have much fear of one. Therefore it seems likely that in their early flying days they might still be inclined to act in this way, and if so, any encouragement to fly which they received from their elders would be of assistance to them. It is noteworthy that the younger birds which I caught were not thus encouraged to run. The public attention, in this case, seemed concentrated on myself.
Terns vary much in the degree of resistance, or rather of evasion, which they offer to the attacks of the skuas—always I am speaking of the smaller of the two species. I have often seen them get off scot-free, without losing their fish, and, as before said, this has always seemed to me to be because of their persistency in holding out, and not at all on account of their superior speed. I have advanced a theory as to why the skuas should not actually attack the terns on these occasions, as they do not seem to me to do, and if there is any truth in it, we here see a road along which a certain number of the latter might become free of the tyranny under which they now suffer. It is doubtful, however, whether these more obstinate birds would gain, in this way, a sufficient advantage over the others to allow of natural selection coming into play. They could carry, no doubt, more fish to their young, but here, at least, the skuas seem hardly in sufficient numbers to make the difference a working one. With many birds, however, a similarly acquired change of habit would mean the difference between life and death. I remember once passing unusually close to a cock pheasant, which remained crouching all the while, though nineteen out of twenty birds would, I feel sure, have gone up. It struck me, then, that as all such pheasants as acted in this way would have a greater chance of not being shot than the others that rose more easily, whilst these latter were constantly being killed off, therefore, in course of time, the habit of crouching close ought to become more and more developed, and pheasants, in consequence, more and more difficult to shoot. Some time afterwards I met with some independent evidence that this was the case, for a gentleman who shot much in Norfolk, remarked, without any previous conversation on the subject, that the pheasants there had taken to refusing to rise, and that this unsportsmanlike conduct on their part was giving great trouble and causing general dissatisfaction. That was his statement. He spoke of it as something that had lately become more noticeable, but only, as far as his knowledge went, in Norfolk, which, I believe, is an extremely murderous county.
Beyond this I have no knowledge on the subject, but I feel sure that a gradual process of change and differentiation is every day going on amongst numbers of our British birds. I believe that I have myself, here and there, seen some traces of it, and my idea is that greater pains ought to be taken to collect evidence in this and similar directions. Along all those lines where fluctuation has been observed, or where modification might, in course of time, be expected, the present truth should be most carefully made out, and having been accurately recorded and published, observation, after a certain length of time, should again be focussed on the same points, and this being renewed every ten, twenty, fifty, or a hundred years, the results could be compared. For instance, our green woodpecker feeds now largely upon ants in their nests, whilst it both fights and copulates upon the ground. How interesting would it be if we had a continuous record of observations of this bird's habits, dating, say, from William the Conqueror or the days of the Saxon Heptarchy, and if we found that no mention was made of these peculiarities, by the field naturalists of those times, but that they first began to be doubtfully recorded in the reign of Henry the Fifth, or Richard the Third. No doubt a connected chain of evidence of this kind will gradually grow up, owing to the accumulation of works of natural history, but it would, I think, be a great deal more satisfactory if the object were kept steadily in view, and I am quite sure that observations made in this spirit would produce much more interesting matter than that which is to be found in the ordinary bird or beast book. For the great idea would then be to compare the present with the past habits of any creature, in order to see whether, or in what degree, they have changed, and this could only be done by continual re-observation, which would assuredly lead to novelty of some sort, instead of mere repetition, which is what we have now; and not only so, but the thing that is so constantly repeated seems often to be founded either on nothing, or nothing that one can get at. Take, for instance—but no, that would lead to twenty more pages at the least, and I want them for something better.
ENCHANTED CAVERNS
A
ALONG the bolder coast-line of this island, where the cliffs, without being very high, are steep and frowning, there are some remarkable caves, which I to-day visited with Mr. Hoseason, in his boat—he having sailed over from Yell Island. To me, at least, they seemed remarkable, principally by reason of the various and vivid colours which the rock perforated by them begins to display as soon as their entrance is passed. This rock, as elsewhere in the Shetlands, is sedimentary, but broken here and there with veins of quartz, often of considerable thickness, which seem to have been shot up in a molten state and to have afterwards cooled—"seem," I say, for I have no proper knowledge as to their geological formation. This quartz, which when exposed to the light of day is white or whitish, is here of a deep rust-red, and this, distributed in long zigzag lines or meanderings, is sufficiently striking, but nothing compared to the much brighter reds, the lakes, and brilliant greens with which the interior of the cavern is, as it were, painted; so that the whole effect, lit up by the candles which we used as torches, resembled, in a surprising and quite unexpected way, those highly coloured and very artificial-looking representations of natural scenery which one sees on the stage—in pantomimes more particularly or on some very florid drop-scene. These colours are due to some low form of vegetation which is spread like a wash over the face of the stratified rock, but it seems surprising, since one is accustomed to associate colour with light, that in the absence of all sun they should not only exist, but be so very brilliant. I have never seen anything like such vivid hues on the surface of rock or cliff exposed to the light of day, nor, indeed, in any landscape, if flowers and the autumn tints of leaves are excluded. Gaudily painted stage scenery, some enchanted or robber's cavern in a pantomime—Ali Baba's, for instance—is really the best comparison I can think of, nor shall I ever again think these exaggerated. Nature is really harder to outdo or burlesque than one may fancy—even on the stage, where the effort is so constantly, and, one would swear, successfully made.
In shape these caverns are long and narrow—throatal, one might call them—and the sea, with the many weird and uncouth noises that it makes as it licks, tongue-like, in and out of them, helps to suggest this resemblance. Though their height is really but moderate, yet, owing to the narrowness of their walls, they have the appearance of being lofty, especially near the entrance, or where, after descending till it nearly reaches the water, the roof is suddenly carried up again. For the most part, however, the height decreases gradually, with the breadth, till at length the cave ends in a low, dark tunnel, which the sea almost fills, and up which the boat can no longer proceed. Yet far beyond, where all is opaque darkness, one still hears the muffled wash and sob of the waves as they ceaselessly eat and eat into the hidden bowels of the rock. As the whole force and vastness of the ocean lies beyond this little tip of its tongue, to where may not such burrows extend? and might not, by a knowledge of their position and the direction in which they run, some inland towns be supplied with the blessing of sea-water?