Feathers

Feathers, the distinctive covering of Birds (q.v.), developed like the hair of Mammals and the scales of Reptiles and Fishes as outgrowths from the skin. Those which determine the shape of a bird are called contour-feathers or penncv, but except in the ostrich (q.v.) and its close allies, the Penguins, and a few other birds, these are not distributed evenly over the body, but in patches called pterylce, and between these the skin is either bare or covered with down, and these interspaces are called apteria. In many birds powder-down patches occur; these are tracts covered with small down feathers, giving off a white or bluish dust, the origin of which is not satisfactorily established

(Nitzsch: Pterylography). Feathers are of various kinds: the most important are the contour-feathers, consisting of a main shaft or stem, divided into the true shaft or rachis (a), and the quill or calamus (d).

From the former radiate the barbs or rami or radii (c c), and these, with the true shaft, form the vane or vexillum. The spaces between the barbs are filled by the barbules (c1), which bear the same relation to the barbs that these bear to the main stem. Generally speaking, the ends of the barbules are hooked, so that those springing from one side of the barb interlock with those of the barb next above or below, and it is to this arrangement that the web-like structure of each side of the vane is due. Barbules, however, do not occur in any of the feathers of the Cursorial Birds, and only in the contour-feathers of other birds. In many feathers there is an accessory vane, called the aftershaft or hyporachis (b) springing from the under side, near where the quill passes into the true stem. This aftershaft may be as long as the vane, though it is generally much smaller, or it may be reduced to a mere downy tuft. When the barbs are soft and free, the feathers are called plumes (pennoplum.ce), or down feathers (plumulee), according as the shaft is largely developed or not. A feather with a long shaft and small vane is called a filoplume.

Feathers are developed within sacs from the surface of conical dermal papillee, by a process that Professor Huxley compares to casting in a mould, and appear first as embryonic down-feathers, which are soon replaced by the permanent feathers formed in a similar way. The life of a feather is generally only a year, when the nutrient pulp in the quill decays, and the feather dies and is shed. This process of shedding the feathers generally takes place when the breeding season is over, and is called moulting.

Besides their uses as body covering and means of flight, feathers serve as sexual attractions, and in some cases as means of producing love-calls, as the "bleating" of the snipe, the rattling of the quills by peacocks and birds of paradise, and the "drumming" of the North American grouse.

The commercial importance of feathers is very great. The down of the Eider-duck (q.v.), and the feathers of swans, geese, and poultry are very largely used, the first for quilting articles of clothing, and the second for stuffing beds and pillows, and cushions. Despite the Selborne Society (q.v.), vast numbers of gay-plumaged birds are annually killed for trimming hats and bonnets, and the plumes of the Ostrich and the Marabout Crane figure for a large sum in our list of imports, while other birds are warred upon to provide muffs and feather-trimmings. [Quill.]