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Feathers and Flight

Aviculture

Pensacola Jr College

FEATHER STRUCTURE

Feather Structure

• Made out of keratin (a protein)

• Shaft = central structure

– Calamus = hollow shaft base, no barbs

– Rachis = part of shaft that supports the vane

• Vane = the “functional feather”, one on each side of rachis

Feather Structure

• Vane

– Barb = primary branches off the rachis

– Barbule = microscopic branches off the barb

– Barbicels = hooklike structures on the barbule, zip barbs together

– Afterfeather = barbs at base of vane without hooks, for insulation

FEATHER TYPES AND LOCATIONS

Types of Feathers

• Vaned

– contour and flight types

Vaned Feather (contour)

Vaned Feather (flight)

• Down

– no or short rachis, loose barbs/barbules

– traps air in insulating layer next to skin

Down Feather

• Semiplume

– large rachis, loose veins

– insulation, aerodynamics, courtship

Semiplume Feather

Types of Feathers

• Filoplume

– Hairlike, fine rachis with thick tip and terminal tuft of barbs

– Located near flight feathers

– For aerodynamics (adjusting flight feather positions)

Filoplume Feather

Types of Feathers

• Bristles

– Stiff tapered rachis, a few barbs at the base

– Generally only on the head

– Sensory and protective functions

Bristle Feather

Vaned Feathers

• Contour feathers

– Cover most of body, including base of wings

– Various functions

• Flight feathers = long feathers on wings and tail

Flight Feathers

• Remiges = wing flight feathers

– Primaries = distal flight feathers (attached to hand), usually 10, provide forward thrust

– Secondaries = proximal flight feathers (attached to arm), may be modified for display

Flight Feathers

• Rectrices = tail flight feathers

– Attached to pygostyle

– Usually 12

– For steering and braking

Remiges

Remiges and Coverts

Rectrices

Where are the feathers?

• Feather tract

– Dense concentration of feathers

– Typically 9 major tracts on the body

• Apteria

– Regions of naked skin between the tracts

Tracts and Apteria

FLIGHT

Weight vs. Lift

• The bird’s weight results in a downward gravity pull, countered by:

• Upward lift

– Airfoil shape of bird’s wing

– Faster air speed over curved upper surface of wing than under surface

Drag vs. Thrust

• Drag = negative forces opposing forward movement

– Induced drag = caused by air turbulence around wing

– Profile drag = caused by friction between air and body

• Countered by:

• Thrust = forward power due to downward wing beat

Aerodynamics

Aspect Ratio of Wing

• High aspect ratio

– Long narrow wings

– Provide lots of lift, low drag

– Used for gliding

– Must fly fast to avoid stalling from induced drag, but low at wing tips

• Medium aspect ratio

– Can be used for widest variety of purposes

Aspect Ratio of Wing

• Low aspect ratio

– Short and rounded wings

– Must flap wings to provide thrust, due to high profile drag and high exposure to wingtip induced drag

– Good for fast takeoffs and high maneuverability

Phillippine Eagle

• Watch for slots (“winglets” decrease induced drag)