Birds have a variety of feathers that serve different purposes. Feathers provide birds with flight, thermal regulation, waterproofing, camouflage, courtship displays and other functions. There are several main types of feathers that are classified according to their location and structure.
Types of Feathers
The main types of feathers are:
- Contour feathers – Flight and body feathers
- Down feathers – Fluffy undercoat feathers
- Semiplumes – Intermediate feathers with features of both contour and down
- Bristles – Stiff feathers around the mouth and eyes
- Filoplumes – Hair-like feathers with sensory function
- Powder down – Feathers that disintegrate to produce powder
Contour Feathers
Contour feathers are also called flight feathers or pennaceous feathers. They have the following characteristics:
- Firm, smooth surface
- Central shaft (rachis) with side branches (barbs) and hooks (barbules)
- Allow air to flow over wing and tail feathers for flight
- Streamlined and asymmetrical
There are several types of contour feathers:
- Flight feathers – Long, stiff feathers on wings and tail that generate lift and thrust
- Tail feathers – Help control flight, sometimes elaborate for displays
- Primary coverts – Overlap and cover base of flight feathers
- Secondary coverts – Overlap secondary flight feathers
- Marginal coverts – Cover the edges of the wings and help streamline
- Alula feathers – Thumb feathers that provide extra lift
Down Feathers
Down feathers are soft, fluffy feathers with the following features:
- Fine loose barbs without hooks
- Barbs branch from all sides of the shaft
- Provide excellent insulation
- Trap air within and between feathers
- Grow close to the skin underneath contour feathers
Semiplumes
Semiplumes have features of both contour and down feathers:
- Shaft with fine side branches
- Provide some insulation
- Usually concealed by contour feathers
Bristles
Bristles are stiff feathers that occur around the mouth and eyes. They have the following characteristics:
- Very short
- Stiff and hair-like
- Protect eyes from debris and insects
- Found around nostrils and beak
- Help birds feel when handling food
Filoplumes
Filoplumes are hair-like feathers with sensory function. They have these features:
- Hair-like with few barbs
- Embedded among contour feathers
- Transmit information on feather placement and skin stimulation
- May help birds preen and position feathers
Powder Down Feathers
Powder down feathers continuously disintegrate to produce a fine powder. Characteristics include:
- Only a few barbs at growing tip
- Help waterproof and maintain feathers
- Powder spreads onto feathers during preening
- Found in some specialized bird groups like herons and parrots
Feather Locations on a Bird
Different types of feathers are found in specific tracts and locations on a bird’s body. These include:
Remiges
Remiges are the long, stiff flight feathers on the wings. They include:
- Primaries – Attached to hand/digit bones, 10-11 primary feathers
- Secondaries – Attached to forearm, 11-20 secondary feathers
- Tertials – Inners secondaries arising from humerus
Rectrices
Rectrices are the tail feathers responsible for flight control. Characteristics include:
- 6-8 paired feathers attached to tail bone
- Vary in number and shape between species
- Central pair vital for steering and braking
Contour Tracts
Tracts of contour feathers cover the body in specific patterns. Major tracts include:
- Pterylae – Bare strips where feather tracts join
- Spinal tract – Runs down the midline
- Ventral tract – Covers the underside
- Femoral tract – Runs down the thigh
- Crural tract – Covers the lower leg and feet
Downy Feathers
Downy feathers occur underneath the contour feathers for insulation. They are found:
- Closest to the skin on most of the body
- Most dense on chest, belly, sides and thighs
- Create a layer of trapped, insulating air
Functions of Different Feathers
The various feather types serve specialized functions for birds:
Feather Type | Functions |
---|---|
Flight feathers | Generating lift and thrust for flying |
Tail feathers | Steering, braking and stability in flight |
Down feathers | Trapping insulating air against body |
Contour feathers | Streamlining body profile for flight |
Bristles | Protecting eyes and sensing food |
Filoplumes | Sensing feather placement for preening |
Powder down | Waterproofing and feather maintenance |
Conclusion
Birds have a range of specialized feather types that serve important functions related to flight, insulation, sensory information and feather maintenance. The major categories are contour feathers, down feathers, semiplumes, bristles, filoplumes and powder down. Each feather type is located in specific tracts on the wings, tail, and body according to its aerodynamic or insulating role.
The precise structure and placement of feathers allows birds to regulate air flow, body temperature, sensation and feather condition as they fly, swim, dive, display and go about life as feathered dinosaurs. Feathers are a unique evolutionary innovation that have allowed birds to successfully diversify and populate almost every habitat on Earth.