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 out of 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, or _kameel-dorn_ of 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 said to 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 swarms and 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) nobody seems 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
his _Birds 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 its _modus 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 have never 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 forms a 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 nest with 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—just as 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.