This document discusses flight adaptations and the mechanism of flight in birds. It describes the key morphological adaptations birds have developed for flight including their streamlined bodies, lightweight feathers, modified forelimbs that form wings, and other adaptations. It also discusses important anatomical modifications such as their lightweight skeletons, strong breast muscles, and efficient respiratory and circulatory systems. Finally, it explains how birds generate lift through their airfoils and use a downward power stroke and upward recovery stroke of their wings to fly through flapping.

1. Flight adaptation and
flight mechanism in
birds
Presented by:- Manish Kumar
Dash
+3 2nd yr. Sc. (Zoology)
Roll:- BS12-004

2. Key Points
 Adaptation
 Flight Adaptations in birds
I. Morphological adaptations
II. Anatomical adaptation
 Some terminology related to flight
 Mechanism of flight

3. Adaptation
 Any alteration in the structure or function of an
organism or any of its parts that results from
natural selection and by which the organism
becomes better fitted to survive and multiply
in its environment.
 Greater the degree of adaptation- more is the
deviation from the normal morphology.

4. Flight adaptation in birds
 Morphological adaptations
 Anatomical adaptations

5. Morphological adaptations
 Body contour
I. Spindle shaped body to ensure least wind resistance.
II. High position of light organs (lungs and air sacs) and low
position of heavy muscles, sternum, digestive system.
III. Low Centre of gravity (average location of weight of an object.)

6.  Presence of feathers
I. Makes the body stream-lined and reduces the friction to the
minimum.
II. Very light, hardly adds weight to the bird.
III. Serves as a blanket enveloping air around the body and adds
buoyancy.
IV. Feathers of wings increases the surface area for striking the air.
Morphological adaptations (cont.)

7.  Forelimbs modified into wings:
forelimbs becomes modified into unique and powerful propelling organs,
which propel the body high up in the air.
 mobile neck and beak:
modification of forelimbs is compensated by mobile neck and beak.
enables the bird for feeding, nest-building, offence and defense, preening,
etc.
 Bipedal locomotion: hind limbs supports the body weight and acts as
locomotory organs in the ground.
Morphological adaptations (cont.)

8.  Perching
strongly developed muscles
so modified that when a bird
sits in a perch, the toes
automatically grips the perch.
 Short tail and tail feathers
serves as a rudder during
flight and assist in steering,
lifting and counterbalancing.
Morphological adaptations (cont.)

9. Anatomical modifications
 Endoskeleton:
I. light and provides large
surface for attachment of
muscles.
II. Bones are pneumatic filled
with airspaces, the
extension of air sacs.
III. Skeletal framework is
compact, centralized and
relatively rigid due to fusion
of bones.

10. Anatomical modification (Cont.)
 Muscles of flight
muscles on the back are much reduced and flight muscles on the
breast are strongly developed.
 Digestive organs
digestive system is efficient, rectum reduced and never stores the
undigested food because they cannot afford extra burden of faeces,
hence is immediately got rid.

11. Respiratory System
Air in the bird respiratory system passes through in two breath cycles.
• On the initial inhalation air is passed through straight ducts, the bronchi and
mesobronchi, to posterior air sacs.
• The following exhalation moves this air into the parabronchi of the lungs.
• The second inhalation moves this air on into the anterior air sacs. The second
exhalation then passes the air through the bronchi and out of the system.

12. Anatomical modification (Cont.)
 Circulatory system
heart is large and efficient
complete separation of pure and impure blood
 Reproductive system
single ovary and an oviduct in female is a weight-reducing device.

13. Airfoil
Lift
Gliding
Drag
Flapping
Terminology

14. The wings provide lift by creating a situation where the pressure above the
wing is lower than the pressure below the wing. Since the pressure below the
wing is higher than the pressure above the wing, there is a net force upwards.
To create this pressure difference, the surface of the wing must satisfy one or
both of the following conditions. The wing surface must be:
• Cambered (curved); and/or
• Inclined relative to the airflow direction.
EXPLANATION OF HOW IT WORKS
Airfoil

15. Lift
 Lift force is produced by the action of air flow
on the wing, which is an airfoil. The lift force
occurs because the air has a lower pressure
just above the wing and higher pressure
below.

16. Gliding
 When gliding, birds obtain both, a vertical and
a forward force from their wings. This is
possible because the lift force is generated at
right angles to the air flow. The lift force,
therefore, has a forward component that
counteracts drag.

17. Drag
 Apart from its weight, there are three major
drag forces that impede a bird’s aerial flight:
frictional drag (caused by the friction of air
and body surfaces), form drag (due to frontal
area of the bird, also known as pressure
drag), and lift-induced drag (caused by the
wingtip vortices). These forces are reduced by
streamlining the bird’s body and wings.

18. Flapping
 When a bird flaps, its wings continue to
develop lift, but the lift is rotated forward so
providing thrust, which counteracts drag and
increases its speed.

19. Mechanism of flight
 During flight the wings become unfolded, stretched and
raised vertically upwards.
 These then move downward and forward (down stroke) and
finally upward and backward (up stroke).
 Downstroke is achieved by the action of pectoralis minor,so
that the wing is lowered down. The wing is raised by the
contraction of pectoralis minor, and other muscles.
 During downstroke, the wing is thrust downwards like an oar
impermeable to air. It moves forward and vertically upwards
with little air resistance for the next powerful downstroke.
 The body moves forward in upstroke.

20. Flight mechanism