16. Varieties of Feathers
Feathers grow in definite areas on the body. These feathered areas or strips are known as pterylae. Bare spaces in between are called apterylae. Feathers are divided into four types: contour feathers, hair feathers, fluff feathers, and down feathers.
a. Contour feathers. Contour feathers are large feathers covering the pigeon’s body. When the bird is not in flight or excited, they lie close to its body, normally overlapping and presenting a smooth outer surface. The larger ones are the flight and tail feathers. The average pigeon has 12 main tail feathers; on each wing there are 10 primary flights and 12 secondary flights. The bases of these large feathers are covered by shorter feathers called coverts. These give a rounded, smooth, and continuous line to the body.
The main tail feathers act as a rudder in flight, controlling the bird’s direction. Flying is possible because every flight feather overlaps, presenting a solid surface on the downbeat of the wing. Besides, flight feathers provide lift and pull for the bird’s propulsion. On the upbeat of the wing, the large flight feathers rotate in such a manner as to cut through the air with little resistance, and at the same time to permit escape of air.
The general structure of a contour feather can be best observed in a primary flight from the wing or a large rectrix from the tail. The stiff, hollow, cylindrical portion emerging from the skin is called the quill. The bare quill proper extends only to the webbed portion of the feather. It has a small hole (inferior umbilicus) at the end, penetrating the skin. Nourishment for the feather passes through this opening. The expanded portion of the feather, from the tip to the quill, is known as the vane. The central portion of the vane, which is called the shaft, is solid. Extending laterally from the shaft is a web or webbing composed of barbs or rays. These rays are blade-like in structure. The web of most feathers is generally wider on one side of the shaft than on the other. The barbs are connected by a series of cross structures called barbules which can be seen only with the aid of magnifying lens. To see the barbs, however, apply a slight tension on the webbing of the feather, causing it to spread apart. The invisible barbules will split if too much tension is applied. Barbs can be repaired so that little or no evidence of the split can be detected, by stroking the feather between the index finger and thumb. Pigeons repair a split in the barb by squeezing oil from the oil duct with their beak, and then spreading it on the injured feather.
Feather textures vary greatly with the breed of the bird and the part of the body from which they grow. When selecting homing pigeons, try to select those with strong, firm feathers.
b. Hair feathers. Also known as filoplumes, hair feathers are hair-like structures interspersed among the regular body feathers. They are so fine that they are usually overlooked.
c. Fluff feathers. Sometimes called semiplumes, fluff feathers are soft and fluffy because of the absence of a rigid feather shaft and barbules in their web. The barbs are also long, soft, and fluffy, and present a downy appearance. Fluff feathers grow only on certain parts of the body.
d. Down feathers. Down feathers are the soft, hairy, yellow feathers on young pigeons. They are extremely fine, almost filamentous in structure. These feathers drop off all through the period of the young bird’s growth; a few, however, may remain after complete feathering has taken place.