Birds have feathers covering their bodies that serve a variety of important functions. The feathers help birds fly, keep them warm, aid in courting rituals, and provide camouflage. But what exactly are the feathers called? Let’s take a closer look at the names and types of feathers found on birds.
Types of Feathers
There are several types of feathers that cover a bird’s body:
- Contour feathers – These are the feathers that form the shape of the bird and cover the entire body. They create a smooth, aerodynamic surface.
- Down feathers – Down feathers are soft, fluffy, and very close to the skin. They help insulate the bird and retain body heat.
- Filoplumes – Filoplumes are hair-like feathers with few barbs. They are sensory receptors that detect air movements.
- Flight feathers – The wings and tail feathers (rectrices) involved in flight. They are asymmetrical and help provide thrust and lift.
- Bristle feathers – Stiff, bristle-like feathers around the mouth and eyes. They protect the openings.
- Powder down feathers – Special down feathers that continuously grow and disintegrate into a powder that helps condition the other feathers.
Contour Feathers
Contour feathers form the outermost smooth layer that covers a bird’s body. They help define the bird’s distinctive shape and provide a streamlined surface important for reducing drag during flight. Contour feathers have stiff central shafts with many barbs extending off each side. The barbs hook together with barbules to create a tight vane surface. This gives the feather rigidity and strength.
Contour feathers grow in organized rows called pterylae with bare spaces between them called apteria. They come in slightly different shapes and sizes depending on their location on the body.
Types of Contour Feathers
- Uppertail coverts – Smaller contour feathers covering the upper side of the tail base
- Undertail coverts – Contour feathers covering the underside of the tail base
- Thigh feathers – Contour feathers on the upper part of the thigh or leg
- Flank feathers – Contour feathers on the belly and sides beneath the wings
- Breast feathers – Distinctive contour feathers covering the breast area
- Shoulder feathers – Sometimes colorful or iridescent contour feathers on the shoulder
- Lesser upperwing coverts – Rows of smaller contour feathers covering the upper side of wrist/forearm area
- Median upperwing coverts – Larger contour feathers halfway along the upper wing
- Greater upperwing coverts – Largest contour feathers at the upper wing tip
- Alula feathers – Small contour feathers attached to the alula or “bastard wing”
- Primary coverts – Special contour feathers covering the upper side of primary flight feathers
- Greater underwing coverts – Large contour feathers on underside of wing-tip
- Axillaries – Contour feathers in the armpit area
- Rectrices – The tail feathers involved in flight
The specific names help ornithologists precisely identify the different contour feathers on a bird body. Even within a type, the shapes and patterns create unique identifying features.
Down Feathers
Down feathers are small, soft, and fluffy. They lie hidden beneath the contour feathers and are not visible externally. Down feathers lack stiff central shafts, so the barbs extend out freely in all directions from the base. This allows them to trap air and create excellent insulation to keep heat close to the skin.
Baby birds or nestlings have special natal down feathers that initially help keep them warm. As the birds age and develop flight feathers, a layer of down feathers remains next to the skin. Water birds like ducks and geese have especially thick down layers since they swim in cold water.
The trapped air within down also helps provide cushioning and buoyancy for water birds. Humans have long utilized down feathers from ducks and geese to stuff pillows, bedding, and coats. The fluffy softness comes from the special structural properties of down.
Filoplumes
Filoplumes are hair-like feathers with just a few barbs at the tip. They are found scattered among the contour feathers. Filoplumes do not participate in flight or insulation. Instead, they have sensory nerve receptors that detect air movements around the bird.
Information from the filoplumes allows birds to quickly adjust the positioning of their flight feathers and respond to changes in airflow. Filoplumes sense turbulence and airspeed, signaling the bird to spread or fold its feathers accordingly.
Researchers believe filoplumes may also detect prey movement, triggering a rapid response strike. The hair-like feathers are an important sensory component of a bird’s flight and hunting abilities.
Flight Feathers
The flight feathers are the specialized asymmetrical feathers on the wings and tail that provide the thrust and lift for flying. They grow from specific follicles and have stiff central shafts with vanes that interlock together.
There are several types of flight feathers:
- Primary feathers – Attached to the “hand” area and the most important for flight. There are usually 10 primaries numbered descendantly from the wrist joint.
- Secondary feathers – Attached to the forearm and essential for providing surface area and lift. There are usually 10-20 secondaries.
- Alula feathers – Attached to the alula or “bastard wing” which helps stabilize airflow over the wing.
- Rectrices – The tail feathers involved in controlling speed and maneuverability.
The asymmetry of the feather vanes produces aerodynamic properties when air flows over them. The feather’s shape causes air to flow faster over the narrow top surface, creating lower pressure. This generates the lift needed to fly. The broader, curved lower surface produces some thrust as air flows across it.
By controlling the fanning and angles of their flight feathers, birds can alter the lift and thrust produced. This allows them to take off, glide, soar, and maneuver through the air. The flight feathers are a marvel of natural engineering!
Bristle Feathers
Bristle feathers lack barbules, so the barbs stick out singly from the central shaft. This creates a stiff, bristly texture. Bristle feathers grow in small clusters around a bird’s eyes, mouth, and nostrils.
The bristly texture helps protect and seal these facial openings from debris. Bristle feathers around the mouth also help direct food items into the mouth. In some species, bristle feathers over the nostrils may help filter dust and other particles from inhaled air.
Powder Down Feathers
A few groups of birds, including herons, parrots, and hornbills, have special powder down feathers. These feathers continuously grow from the same follicle and then break down into a fine powder. The bird spreads the powder throughout its plumage by preening.
The powder helps clean and condition the feathers to maintain their function. It absorbs dirt or oils and allows the bird to “powder” itself to stay clean and dry. Powder down feathers are rare but provide a useful maintenance role for some species.
Colors and Markings
While most feathers are white or gray, some contain pigments like melanins and carotenoids that create colorful patterns. The barbs and barbules of feathers reflect light in ways that produce iridescent or metallic sheens in some species. Feather colors and patterns play an important role in camouflage and courtship displays.
The specific colors and markings of the feathers help identify different bird species. Even within a species, the plumage can indicate age, sex, and seasonality. The variety of feather types and their specialized structures allow birds to inhabit diverse environments and exhibit amazing flight capabilities.
Molting
Since feathers are dead structures, they gradually degrade from use and need to be replaced periodically. This feather regeneration process is called molting. Birds molt at least once per year to replace old, worn feathers.
Molting happens in a predictable sequence over several weeks or months. The bird sheds feathers symmetrically between the left and rights sides so flight ability is maintained. Contour feathers molt sequentially across the body, while flight feathers are carefully molted from the inside wing outwards.
The timing of molting cycles depends on the species and seasonality of food resources. Molting requires extra energy, so it is carefully synchronized with the annual life cycle. Understanding the molting sequence and variations between types of feathers provides insight into the biology and evolution of birds.
Conclusion
Birds have a variety of feather types that serve specialized functions – from flight and insulation to sensory reception and courtship displays. The many names for bird feathers help identify their precise placement and roles in avian biology. While feathers may all look similar to the casual observer, their diversity and complexity are key to the success of birds occupying habitats worldwide.
