Feathers are made of beta-keratin proteins and are the most distinctive feature of birds. They play key roles in insulation, flight, coloration and other functions. Feathers have a central rachis with barbs and barbules extending laterally. The barbules interlock in different ways to form different feather types - the plumulaceous downy region at the base for insulation and the pennaceous outer region with strong hooklets for structure. Different feather types serve different purposes like flight, swimming or display.

2. Advanced Ornithology
by
Maryam Riasat
BIRD STRUCTURE AND FUNCTION
(FEATHERS)

3. Feathers
 Feathers are the most
distinctive feature of
avian anatomy
 Specialized filament
structures of the skin
attach to bird’s skeleton
 Collectively referred as
plumage

4. Primary role:
o Insulation
o Aerodynamic (Role in flight)
o Coloration
Secondary role:
o Swimming
o Sound production
o Cleanliness
o Camouflage
o Courtship

5. Feathers Structure
 Feathers consist of a fibrous protein polymer
mainly beta-keratin
 Beta-keratins have some mechanical properties
similar to those of the alpha- keratins found in the
skin of all vertebrates
 Beta-keratins are unique to reptiles and birds,
make up most of the hard structures of reptilian
skin and the leg scutes, claws, and beaks of birds
 Feather keratins are a special class of beta-keratins
that are characterized by a small deletion in their
molecular sequence

6. There are different kinds of feathers but not all
types of feathers provide role in aerodynamics
Flight feathers Contour feathers
Contour feathers
Type of feather help in flight

7. Contour feathers

8. Primary features of contour feather
The primary features of a typical contour feather
are a long central shaft and a broad flat vane on
either side of this shaft
Vane
 The flat part on either side of the shaft of a
feather
Calamus
 The hollow inner portion of the feather shaft that
lacks barbs and attaches to the skin
 Held in the feather follicle on the skin of the bird

9. Rachis
 The rest of the shaft after the calamus called as
rachis
 Filaments of barbs attached with rachis
Barb
 An individual strand of feather material
extending laterally from the rachis
Ramus
 Each barb consists of a tapered central axis called
as the ramus, with rows of smaller barbules
projecting from both sides

10. Barbule
 The barbs possess further branches — the
barbules
 The cells may be simple or may bear
projections called barbicels
Barbicel / Hooklets
 The small hook-bearing processes on a
barbule of a feather
 Hook like structures present on barbules

13. Plumulaceous vane
 Each vane of a typical body feather grades
from a hidden and fluffy basal part, provides
insulation to an exposed outer part
 The barbules on the barbs at the base of the
body feather are long, thin, and flexible and
do not have barbicels
 With their similarly thin, flexible parent barbs,
they create a downy or plumulaceous feather
texture

14. Pennaceous vane
 The outer part of the vane is a firmly textured
and tightly interlocking which forms
pennaceous structure
 The outer vane is based on the interlocking
arrangement of pennaceous barbules
 Well-developed hooklet barbicels are present
on the pennaceous barbules

15. Afterfeather
 The body feathers of some birds
include a secondary structure
called as afterfeather or
aftershaft
 It is a mirror-image shaft and
vane, attached to the same
calamus
 The barb and barbule structure of
afterfeathers is typically
plumulaceous, with rare
exceptions
 The afterfeather's primary
function is to enhance insulation