William Pycraft and James Paton

“ Thus, in flight, the air passes through the wing as it is raised, while in the downstroke the feathers are forced together to form a homogeneous surface.
Birds which fly much have the outer primaries of great length, giving the wing a pointed shape, as in swifts, while in species which fly but little, or frequent thickets, the outer primaries are very short, giving the wing a rounded appearance. ”

“ The central axis is divisible into two distinct parts,—a hollow, cylindrical, transparent calamus, or “quill,” the base of which is inserted into the skin, and a solid, quadrangular rhachis or “shaft” which supports the vane. At the lower end of the quill is a small hole—the lower umbilicus—through which the nutritive pulp passes during the growth of the feather: while at the upper end, where it passes into the shaft, a similar hole will be found,—the upper umbilicus—and from this the last remains of the capsules which contained the nutritive pulp may sometimes be seen protruding. ”

“ Filoplumes are degenerate structures having a superficial resemblance to hairs, but they always bear a minute vane at the tip. They occur in all birds, in clusters of varying number, about the bases of contour feathers. In some birds they attain a great length, and may project beyond the contour feathers, sometimes forming conspicuous white patches, as for example in the necks of cormorants. In their early stages of development they often possess a large aftershaft made up of a number of barbs, but these quickly disappear, leaving only the degenerate main shaft. ”

“ The body-covering of birds is, without exception, comprised of feathers, and by this character alone birds may be distinguished from all other animals.
The most perfect form of feather is made up of a long, tapering rod, fringed on either side, for the greater part of its length, by a secondary series of slender and tapering rods forming a more or less acute angle with the central axis. This fringe is known as the vexillum or “vane” (fig. 1 a) . ”

“ But where the female differs from the male in coloration the young resemble the female parent.
The physiological explanation of complete disappearance of pigment in adult life, e.g. gannet, is not yet apparent.
At least once annually birds renew their feathers completely by a process known as a moult. Until the new feathers have attained at least half their full length they are invested in a soft sheath, and, as development proceeds, the sheath breaks up from the tip of the Moulting.feather downwards, so that for a time the new feathers have almost a brush-like appearance. ”

“ Only in the cassowary and emu among adult birds is the aftershaft as large as the main shaft.
There are several different kinds of feathers—contour feathers, semiplumes, down-feathers, filoplumes and powder-down. Contour feathers, as their name implies, are those which form the contour or outline of the body, and are all that can generally be seen. Those which form the “flight feathers” of the wing, and the tail feathers, are the most perfectly developed. Semiplumes are degenerate contour feathers. ”

“ The growth of the feathers is, however, certainly affected by the general health of the bird, mal-nutrition causing the appearance of peculiar transverse V-shaped grooves, at more or less regular intervals, along the whole length of the feather. ”

“ As growth proceeds the cells of this middle layer arrange themselves in longitudinal rows to form the barbs, while the barbules are formed by a secondary splitting. At their bases these rudimentary barbs meet to form the calamus. Finally the tips of the barbs break through the investing sheath and the fully formed down-feather emerges.
A part of the pulp and Malpighian cells remains over after the complete growth of the down-feather, and from this succeeding generations of feathers are developed. ”

“ When dry the shafts are pared or scraped down to give the feathers greater flexibility, and the barbs are curled by drawing them singly over the face of a blunt knife or by the cautious application of a heated iron. Dull-coloured feathers are usually dyed black. Feathers which are dyed light colours are first bleached by exposure in the open air. Much ingenuity is displayed in the making up of plumes, with the general result of producing the appearance of full, rich, and long feathers from inferior varieties and from scraps and fragments of ostrich feathers ”

“ Powder-down feathers are degenerate down-feathers which appear to secrete a dry, waxy kind of powder. This powder rapidly disintegrates and becomes distributed over the plumage, adding thereto a quite peculiar bloom. In birds of the heron tribe powder-down feathers have reached a high degree of development, forming large patches in the breast and thighs, while in some hawks, and in the parrots, these mysterious feathers are scattered singly over the greater part of the body.
The nature of the covering of nestling birds is of a more complex character than has hitherto been suspected. ”

“ The down-feathers are generally completely hidden by the contour feathers: they form in many birds, such as gulls and ducks, a thick underclothing comparable to the under-fur of mammals such as the seals. In all cases they are of a loose, soft, “fluffy” structure, the barbs being of great length and slenderness, while the barbules are often long and provided with knob-like thickenings answering to the hooklets of the more perfectly developed contour feathers ”

“ There is also evidence to show that the evolution of brilliant plumage began with the males, and has, in many cases, been more or less perfectly acquired by the females, and also by the young, as for example in the kingfishers, where parents and offspring wear the same livery. ”

“ On the opposite side of the barb the barbules are also ribbon-shaped for about half their length, but the ribbon is curved trough-fashion, so that the whole series of posterior barbules forms a number of deep valleys, and into these the hooklets are thrust so as to catch hold of the upper edges of the troughs, which are set so that the upper edge is towards the upper, and the lower edge towards the under surface of the feather. ”

“ Ostrich farming is one of the established industries of South Africa, and is also practised in Kordofan and other semi-desert regions of North Africa, in Argentina, and in Arizona and California in North America. The feathers are generally plucked from the living animal—a process which does not appear to cause any great inconvenience. ”

“ Feathers which possess strong or stiff shafts cannot without some preliminary preparation be used for stuffing purposes, as the stiff points they present would not only be highly uncomfortable, but would also pierce and cause the escape of the feathers from any covering in which they might be enclosed. The barbs are therefore stripped or cut from these feathers, and when so prepared they, in common with soft feathers and downs, undergo a careful process of drying and cleaning, without which they would acquire an offensive smell, readily attract damp, and harbour vermin. ”

“ As development proceeds the papillae assume a cone-shape with its apex directed backwards, while the base of this cone sinks down into the skin, or rather is carried down by the growth of the Malpighian cells, so that the cone is now sunk in a deep pit. ”

“ The Chinese excel in the preparation of artificial flowers and other ornaments from bright natural-coloured or dyed feathers; and the French also skilfully work fragments of feathers into bouquets of artificial flowers, imitation butterflies, &c. ”

“ The majority of young birds, as is well known, either emerge from the egg clothed in down-feathers, or they develop these within a day or Nestling down.two afterwards. But this covering, though superficially similar in all, may, as a matter of fact, differ widely in its constitution, even in closely related forms, while only in a very few species can the complete history of these feathers be made out. ”

“ They serve to fill up the gap which, in long-winged birds, would otherwise occur during flight between the quill-feathers of the forearm and the body, a gap which would make flight impossible. In short-winged birds these two series are extremely reduced. ”

“ W. P. Pycraft, “The Interlocking of the Barbs of Feathers,” Natural Science (1893) .
On the Colours of Feathers.—J. L. Bonhote, “On Moult and Colour Change in Birds,” Ibis (1900) ; A. H. Church, “Researches on Turacin, an Animal Pigment containing Copper,” Phil. Trans. clix. (1870) , pt. ii.; H. Gadow, “The Coloration of Feathers as affected by Structure,” Proc. Zool. Soc. (1882) ; Newbegin, Colour in Nature (1898) ; R. M. Strong, “The Development of Color in the Definitive Feather,” Bull. Mus. Zool. ”