Feathers of Birds: Structure, Types, & Functions of Feathers

Feathers of Birds

Feathers are the ultimate characteristic of birds. No other (living) animals have them. The qualifier is required due to the fact that feathers have actually now been found in fossil imprints of some dinosaurs and related reptiles. Like the hair on mammals and scales on reptiles, feathers belong to the integument (skin).

All are mainly made up of keratin, which is also the main ingredient of human nails, animal claws, and the scales on the legs and feet of birds. Feathers are impressive structures, both extremely strong and very light. They undergo long flights and are bent and twisted, yet they are hardly ever harmed.

Structure of a Common Feather

To comprehend the structure of a feather, a contour feather which happens on the basic body, wing, and tail, can be considered as typical. A typical contour feather consists of a central axis, primary stem or scapus, and an expanded distal portion, the vexillum or vane.

  1. Scapus (Axis): The scapus is divided into a basal portion, the calamus, and an upper shaft or rachis.

❖ Calamus: The calamus is hollow, tubular, and semitransparent. The base of the calamus remains inserted into a pit or hair follicle of the skin. The calamus opens below by a small opening called the inferior umbilicus, which gets a little, conical, nutritious dermal papilla from the dermis. Another pore, called the remarkable umbilicus, happens on the forward side of the junction of the calamus and rachis.

❖ Rachis: The part of the scapus above the calamus is a rachis. It forms the longitudinal axis of the vane. It is solid, opaque, roughly quadrangular in transverse section, and filled with a closely packed mass of pith cells.

  1. Vane:

❖ The rachis bears a fan-like, webbed, or expanded membranous part of the feather, the vexillum or vane. The vane is divided by rachis into two unequal lateral halves. Its proximal end is wider than the distal end. Each half of the vane is composed of a series of numerous (about 600), parallel, closely spaced, fragile, lateral, thread-like structures called the barbs or rami. The barbs occur obliquely outwards from the two lateral sides of the rachis.

❖ Plumes are always shed or moulted at regular intervals, as a rule yearly after the breeding season.

Types of Feathers

Feathers come in many different shapes, but all of them can be classified into 6 different types of feathers. The plumes we are utilized to seeing are flight and contour. Down feathers are what we use in pillows, quilts, and coats. The other 3 feathers, semi plume, filoplume, and bristle, are not as typical, however still helpful to birds.


Flight feathers

Flight feathers are present in two places on birds: the wings and tail. Flight feathers are long, and on the wings, have one side of the vane broader than the other. They also have more powerful barbules which give them more strength for flight.

Contour feathers

Contour feathers offer shape and color to the bird. They are found everywhere except the beak, legs, and feet. Contour feathers are colored just at the ends (the only part that we see). At its base, a contour feather becomes downy which assists insulate the bird.

Semiplume plumes

Semiplume feathers are a cross between down and contour feathers. Unlike down, they do have actually a well-formed shaft. However, they do not have well-developed barbicels that make them soft. Semiplume feathers are present below contour feathers and are used for insulation.

Down feathers

Down feathers have little or no shaft. They are soft and fluffy. Down feathers help insulate birds by trapping air. Some birds, such as herons, have unique down feathers called powder down which breaks up into a great powder. The bird then spreads this fine powder all over its body to act as a water repellent.

Filoplume feathers

Filoplume feathers are extremely small. They have a tuft of barbs at the end of the shaft. Unlike other feathers which are attached to muscle for motion, filoplume feathers are connected to nerve endings. These feathers send out messages to the brain that provide information about the positioning of feathers for flight, insulation, and preening.

Bristle feathers

Bristle feathers are really stiff with only a few barbs present at the base. Bristle plumes are found around the mouth of insect consuming birds where they function as a funnel. They can also be found around the eyes where they work like eyelashes.

Functions of Feathers

They serve a varied selection of functions which have actually been summed up listed below:

  1. Protection:

Plumes form a light-weight, invulnerable, flexible, resilient, and water-resistant body covering. They protect the underlying tender skin from all types of mechanical, chemical, pathological, and ecological injuries.

  1. Heat Retention:

The birds have a consistent body temperature level which frequently remains between 104 ° and 112 ° F, even in subzero weather conditions. Thus, the plumes serve the most essential function of retention of heat since the plumage forms an effective, non-conducting covering with its innumerable dead air spaces, useful as insulation.

❖ In winter the heat loss is lowered to a minimum by fluffing out the feathers, which increases the depth of insulating material by contributing to the air spaces within the feathery layers.

❖ In warm weather, the feathers are frequently held near the body to enable some escape of body heat.

  1. Camouflaging (Protective Coloration):

The feathers of various birds have rather characteristic protective coloration like the pigmentation of their surroundings, that make them indistinguishable from their regular environments and, thus, serve to safeguard them from their opponents.


  1. Sexual Dimorphism:

Feathers provide protective pigmentation and also sexual display. Sexual dimorphism is common in monogamous in addition to polygamous species. Colors and erectile plumes end up being indication stimuli that evoke or launch particular reactions and entire pattern of behavior in competitors and mates.

For example, on many birds, the crown plumes are modified into crests (peacock), decorative plumes (California quail).