British birds

by W. H. Hudson; Frank E. Beddard

Figs. 2, 3. (After Wray in ‘Ibis’ for 1887.)

B, Barbs; bp, proximal barbules; 1, flange; 2, ‘dog-tooth,’ part of flange; 3, overlapping portion.

Fig. 4.—Portion of two adjacent Barbs. (After Wray in ‘Ibis’ for 1887.)

B, barbs; bd, bp, barbules (distal and proximal).

The most curious modification, however, of the feather is into that structure known as a ‘powder-down.’ These feathers have, as their name denotes, a powdery appearance, which is due to the continual breaking off of the fine ends of the barbs; the feathers themselves are soft, and belong to the variety of feathers which have been described as down feathers. The dusty matter which they give off has been described as ‘dry and yet fatty to the touch.’ They are found in various birds; they do not characterise any one particular group, except the Heron tribe; some Parrots have them, a few Hawks, and certain other genera. It has been said that they are phosphorescent; and it has been suggested that their presence in the heron is of use to it in its fishing. The light, it is thought, attracts the small fishes within reach of the heron’s long bill. But this appears to be one of those exaggerations founded upon actual fact which are so common in natural history.

Another important fact about a feather is its colour. There is no purely white bird in this country and not very many that are chiefly white. But there are some, like the Gulls and the Storks. The nearest approach to an absolutely white bird is the beautiful little Egret, whose plumes are, unfortunately, so much used in feminine adornment. As concerns its feathers, this bird is absolutely white, but other parts of the body are black. A bird that is purely white, not only in the feathers but in the legs and beak, is called an albino. This state of affairs is not commonly met with, but it sometimes occurs; everybody has heard of that contradiction in terms, but actually existent creature, the ‘white blackbird.’ In all these cases there is something wanting in the feather; for white is not a colour—it is the negation of colour, and is due in nearly every case to the scattering of the rays of light which fall upon the object. This happens when the material that is coloured white is broken up into minute fragments separated by air. The froth of the sea or of a brimming tankard is simply due to the entangling of bubbles of air, which scatter the rays of light. The stems of the feathers contain bubbles of air, which bring about a like effect. But the majority of birds are coloured, and, as a rule, perhaps, brightly coloured. We have not in this country many birds which can compare with the gaudy parrots of the East; but brilliancy of hue is by no means wanting in the birds of this and of other countries which enjoy a temperate climate. It used to be said that brilliancy of colour was a characteristic of the tropics. But it is always pointed out, by way of a refutation of that statement, that the Golden Pheasant of China is as gorgeous a bird as any which exists. There are few small birds which are really more brilliant in hue than our Yellow-hammers, Goldfinches, Bullfinches, and some others. We have, it is true, nothing to seriously compete with the Humming-birds; but these birds are found not only in the tropical forests of Brazil, but also in North America and upon the snowy summits of the Andes, and can therefore hardly be used as an instance of the exclusive restriction of brilliant colour to a tropical climate.

The hues of the feathers are due to two causes. In every case where there is colour at all the feathers contain a certain amount of dye, or pigment, as it is more usually termed; this pigment may be alone responsible for the colour of the feather, or it may be only a part of the cause. If the bright blue feather from a Macaw’s wing be roughly pressed so as to injure the surface, the blue colour will disappear from the rubbed place, and will be apparently replaced by a brownish black. The reason for this is that the blue colour is the result of the actual structure of the feather, which requires the underlying black pigment for its manifestation. The crushing destroys that structure and leaves only the dark pigment. The brilliant and varying hues of the soap-bubble and of mother-of-pearl are examples of substances which owe their colour to their structure; and the hues of the bird’s feather are produced by a similar kind of structure. Finely ruled lines engraved upon the feather just below a clear and transparent outer skin are responsible for the tints of different colours. But there are many birds whose colours are entirely due to the pigments. The most interesting instance of this in many ways is an African bird, the Touraco. This bird is green for the most part, but the feathers of the wings are of a magnificent crimson. When the birds take to the wing this gorgeous colour is displayed; before, it is concealed by the overlying feathers. The colouring matter can be easily extracted from the wing, and it forms a solution of a splendid crimson as bright as the substance called cochineal, which is the product of an insect. It was once said that this colour could be, and was as a matter of fact, washed out from the wings of the bird during heavy storms of rain, and that when a touraco was shot and fell into the water it stained the water red, not with its blood, but with the dye from its feathers. This is, however, an exaggerated way of putting the fact that even very feebly alkaline water will dissolve out the colour. Some of the yellows of the woodpeckers and the browns and reds of other birds are solely brought about by the presence of pigments.

In speaking of birds as ‘feathered songsters’ or as ‘feathered bipeds,’ we are a little apt to lose sight of the fact that they are also scaly—an error which is occasionally rectified by the view of an obtrusive pair of legs belonging to the fowl upon the dinner-table. The legs of birds are nearly always scaly; there are a few exceptions or nearly exceptions. For instance, there is a special breed of pigeons with feathered legs; and the sand-grouse, which makes those remarkable and periodical invasions, has legs which are more covered with feathers than with scales.

The possession of scales is one of the most striking points of resemblance between birds and reptiles. At first sight it seems to be almost absurd to attempt to draw any parallel between the active, feathered, hot-blooded bird and the scaly, cold-blooded reptile; yet there are many resemblances, some others of which will be indicated in the following pages. In the meantime we are concerned with the scales. These are flat plates, produced by a horny alteration of the soft underlying skin, which are precisely like those of the lizards and snakes. No other animals possess scales; those of the armadillo appear to be not unlike the scales of reptiles and birds, but they really are not, nor are those of the scaly manis, which are more comparable to closely matted tufts of hair. The scales of a fish are totally different, since they are not formed by the true skin, the epidermis, at all, but by the underlying dermis. In no bird, however, are there scales upon any part of the body except the legs. But one bird makes a near approach to having scales elsewhere. This is the Penguin, the feathers of whose wings are flattened and very scale-like. But the characteristic fringing of the feather can be detected on a careful examination. The penguin uses its wings as paddles to fly under water. A branching and delicate feather would be worse than useless under such circumstances; hence the superfluous fringing of the stem of the feather has been got rid of, and the feather itself has become flattened and lies close to the skin.