CHAPTER IVWONDERFUL BIRDS’-NESTS—A CITY OF GRASS—BIRD WEAVERS AND TAILORS—BIRDS THAT MAKE POTTERY—EVOLUTION IN BIRD-ARCHITECTURE.
WONDERFUL BIRDS’-NESTS—A CITY OF GRASS—BIRD WEAVERS AND TAILORS—BIRDS THAT MAKE POTTERY—EVOLUTION IN BIRD-ARCHITECTURE.
The penguins, like others of the diving sea-birds—our own guillemots and razor-bills, for instance—make no nests. Birds, however, taken as a class, are remarkable, as we all know, for the wonderful structures which they build, to lay and incubate their eggs in, and sometimes, as we shall shortly see, for other purposes as well. Chief, perhaps, amongst these wonderful builders come the weaver-birds, and especially that species which is named,par excellence, the sociable weaver-bird or grosbeak—for most of them are sociable in a greater or less degree. Though not more than about five inches long and of a plain appearance, these little birds, by uniting together, make, perhaps, the largest nest or structure that any bird makes, it being large enough to conceal four or five men from view, if they should get behind it. It is built, however, in a tree, and entirely of a very long, tough, and wiry kind of grass, called Bushman’s or Booschmannie grass, because it is plentiful where the Bushmen used to live—for the grass has outlived the Bushman. This grass the birds pull outof the ground, and when they have got a good bunch of it they fly to the tree they have chosen—which is often the pretty mimosa, orkameel-dornof the Boers—and lay it across a properly shaped branch, so that it hangs down upon either side. Then they plait and weave each row of ends together, and by constantly bringing more grass and continuing the process, pushing it out, as they go, so as to make it bulge, gradually, on each side of the branch, they make, at last, a hollow, thatched structure, narrow at the top, where it is supported by the branch, but getting wider as it descends, like the thatched roof of a cottage, which, indeed, it much resembles. It is higher, however, in proportion to its length, and so has roughly the shape of a beehive or diving-bell; or, again, it may be widened out at the top and made more rounded, so as to resemble the head of a gigantic mushroom. The structure is, of course, continuous all round, the two rows of hanging grass-stems having been woven together by the birds, at either end. Inside this hollow dome, or roof, the actual nests are now placed, each pair of birds building a separate one, though as they are all woven together, the whole of them, with the covering thatch, has the appearance of one structure when finished. The nests descend within the roof, to the same depth, so that the central hollow becomes filled up with a mass of material, within which, however, are a great number of smaller hollows—each one the nest of a pair of weaver-birds—like the cells of a honeycomb, but with wider spaces between each. A sort of thatched honeycomb, indeed—though without the honey—is what the completed structure may most be saidto resemble, but really to complete it, takes many years; for it is not in one season, nor two, that the whole of the roof, or dome, is filled up. Indeed, when it is, it may be surmised that the numerous colony inhabiting it, which may then amount to some two or three hundred souls, or perhaps more, is shortly about to emigrate, since the weaver-birds, like most other ones, do not care to occupy the same nest, for two seasons in succession. Instead, when the breeding-time comes round again they build another one, and it is in this way that the whole space of the dome is gradually taken up, though a large part of it always remains unoccupied. As many as 320 nests have been counted, which would make 640 birds, were there a pair to each; but a considerable number of them—perhaps half—must have been old ones, no longer in use. What proportion such old nests bear to the new ones I do not know, so when I say that a colony of weaver-birds may number some two or three hundred souls only, it is in order to be on the safe side.
But how delightful to see and be able to watch such a colony as this, clouds of the birds continually flying in and out, or clustering together amongst the branches, or on the outside of the thatched roof of their common house, all chirping and twittering, flying off every now and then with a whirr, and descending again with another one. Add to this, the ordinary daily vivacity of the scene, the occasional approach of a hawk or a monkey—a baboon, perhaps, or a whole party of baboons. How great then would be the commotion, hundreds of incensed, twittering little creatures flying out in swarmsand dashing about the intruder, who, being thus mobbed, would probably soon find discretion to be the better part of valour. The hawk, however, might, and probably frequently does, take his toll before going. As in our own country, he is no doubt accustomed to being mobbed, and does not mind it much. With regard to the monkeys, they would be extremely glad to get any of the weaver-birds’ eggs, and still more, perhaps, the birds themselves, but the nest—to give the whole collective structure this name—is built in such a way as to render this difficult. It hangs in the air, and slants outwards as it descends, so that a small monkey getting on the top of it might find it difficult to avoid slipping down, whereas the massiveness of the structure is such as to deter even the baboons from trying to pull it to pieces. Whatever the reason, they do not apparently endeavour to do so. Perhaps the swarm of angry birds alone is sufficient to keep them off, or possibly, being always accustomed to see these great house-like structures amidst the branches, they look upon them as a part of the tree itself. The birds, of course, would not be likely to choose the most exposed branches to build on, but still, judging from the illustrations one sees, these nests cannot be said to be inaccessible. The smaller monkeys, however, are not so very common in South Africa—whilst baboons are less arboreal than monkeys generally are. Some people write, indeed, as if they had given up climbing altogether, but if they had seen them, as I have, walking out along the branches of high trees on the banks of the Limpopo, and on, from tree to tree, they would not go as far as that.However, it is to these two circumstances, as I believe, that these great social nests of the Weaver-birds in South Africa, principally owe their immunity.
Others of the family make separate nests, which they attach to the end of leaves, twigs, small branches, or slender swaying creepers that hang down over water—generally a river—so that they cannot be got at by any monkey, however small, or even by snakes, which are still more redoubtable enemies. These graceful “pendent nests and procreant cradles,” swung and danced by the lightest air, are of all sorts of shapes—rounded, or gourd-shaped, or rounded with a sort of stocking hanging down from it—and are all of them beautifully woven with the stems and blades of various grasses.
In this plaiting of the natural growing grass into a fabric, one might think that the height of bird architecture had been reached, but there is a Tailor-bird as well as a Weaver-bird, and what he does is perhaps even more wonderful, since he uses a needle and thread, his bill doing duty for the needle. Having picked some holes along the edges of two or more leaves that hang near to one another, the bird passes a thread through them, in and out, all the way along, and then draws them together with it, tightening the thread, as we should do, and making a knot at the end of it, so that it may not come undone. It has previously made another knot, or bunch, at the other end of the thread, to prevent that slipping either; but how it does it, or how it makes the thread that it uses (for it is said to manufacture it, not merely to take a fibre or grass-stem, at least not always) nobodyseems to know. As the Tailor-bird is a native of India, and is not shy, but comes into gardens and compounds, where, no doubt, it often builds its nest, this want of information is not much to the credit of naturalists in that country. But perhaps it is a difficult thing to see, however near the bird may come. Jerdon, in hisBirds of India, tells us that “it makes its nest of cotton, wool, and various other soft materials,” and that “it draws together one leaf or more—generally two leaves—on each side of the nest, and stitches them together with cotton, either woven by itself, or cotton thread picked up; and after passing the thread through the leaf, it makes a knot at the end of it.” This sounds as if the nest was made first and the leaves drawn round it afterwards, but nobody would suppose this, or, indeed, that it was possible, so I am not going to believe it till somebody who has seen the bird at work tells me that this is itsmodus operandi.[2]The Tailor-bird is quite small and of sober appearance. It has a long tail though, which, in the illustrations, sticks right up, whilst the beak has a very delicate tactile appearance, almost suggesting a needle, though not quite the kind that we use. There is, too, a certain little dapper, demurely self-satisfied look about the bird—I mean in the illustrations, for I havenever seen it—as if it knew what it could do, and was proud of being able to do it. If it is, nobody, I think, need blame it.
Besides birds that weave or stitch their nests, thus associating themselves, as it were, with two of the oldest and most respectable guilds of human society—there are others that belong to a third guild, and may be called potters, inasmuch as they make theirs of clay, with only a small admixture of other substances. The Oven-bird is, perhaps, the chief of these, a bird allied to our own little tree-creeper, but about the size of a lark. It lives about the banks of South American rivers, and with the mud, or clay, that it finds there, stiffened with grass, bits of straw, or other vegetable fibres, it builds its very remarkable nest, which, “in shape, precisely resembles an oven or depressed beehive,” and is soon baked almost as hard as a brick, by the heat of the tropical sun.
The outer clay wall of this strange nest is nearly an inch in thickness, and, as there are two interior chambers, the size of the whole is very considerable, in proportion to that of the bird. It is, therefore, a conspicuous object in itself, and not the slightest attempt is made by the bird to conceal it. “It is placed,” says Darwin, “in the most exposed situations, as on the top of a post, a bare rock, or on a cactus.” The entrance is at one side, and in the larger of the two compartments, which is the inner one, the nest, which is a soft bed of feathers, is placed. What the outer compartment is used for, or whether it has any special use, I do not know. Wood says that the male probably sits in it, whilst Darwin thinks it merely formsa passage, or antechamber, to the true nest. As to a very learned work written by several learned people, which I am always looking at, and always to little or no purpose, it says nothing, but merely tells you that so and so has mentioned the bird and somebody else said quite a good deal about it—and it evidently thinks this enough, though I don’t.
Then there is the Pied Grallina, an Australian bird that makes a nest which resembles a large clay bowl or pan, and another, called the Fairy Martin, belonging to the same country, whose nest, built wholly of clay and mud, has very much the shape of an oil-flask with a rather short neck, which projects forwards and downwards, and has an aperture at the end, by which the bird enters. Like those of other swallows and martins, these nests are built several together, and are fixed to the face of a cliff or the hollow of a large tree. Our own little martin-nests are not quite so remarkable as these, but they are sufficiently curious, and it is interesting that in the swallow family we at last get to birds which make their nests—I mean, of course, the exterior part—entirely of mud, without any straw or grass being mixed up with it. It is interesting, I think, because my own idea is that mud came first to be used in nest-making, through its adhering to the roots of grasses and water-plants, and that in the bits of straw and fibre, mixed up in the pottery of such accomplished mud-builders as, say, the Oven-bird, we see the last traces of the way in which these structures began. It was watching blackbirds build that first gave me this idea, for the blackbird plasters the cup of its nestwith mud, as the thrush does with cow-dung and rotten wood; yet this mud is procured in the way indicated, and the plants to which it adheres form the bulk of the burden, and are of more importance than it is in the architecture of the nest. Gradually, as I believe, the mud got more and more, and the vegetable alloy less and less, till, at last, in the nests of some species mud only came to be used.
But we reach a further stage where mud has been given up, and something else adopted in its place. Thus the thrush, whose nest, up to a certain point, much resembles that of the blackbird, makes a cup to it, not of mud, but of cow-dung and rotten wood mashed together. That it once used mud, however, but that in civilised lands, rich in cows, the other substance gradually took its place, I have myself little doubt.
Finally, in the nest of the Edible Swallow, or rather Swift, of India and the Malay Archipelago, we have, perhaps, in its way, as wonderful an example of bird architecture as any that exists. These nests are attached to the face of precipices, and both in this and their general appearance resemble those made by the house-martin, who, before there were houses, no doubt chose precipices too. They are open, however, not domed, so that the resemblance is to a martin’s nest about three-quarters finished, rather than to a completed one. Who can doubt, having regard both to their shape and the site chosen for them, that the bird that makes these nests, or rather its ancestors, used, ages ago, to make them of mud. But this mud was mixed with the salivary secretions—justas in the case of the house-martin now—and these becoming, as the glands developed, more and more viscous and glutinous, as well as more copious, began at last to do duty for the original material, so that now they have entirely taken its place. The substance thus used is, at first, in a semi-liquid state, but dries and hardens till it becomes quite solid. On being steeped in hot water, however, it again softens into a sort of jelly, which is made into soup by the Chinese cooks, and eaten with the greatest possible relish by the Chinese epicures.