Chapter 5 - Flight

Question 1

Gravity (Weight)

Answer 1

Will pull the bird downward

Question 2

Drag

Answer 2

The frictional force of air molecules
moving over the surface of the bird. Will slow the
bird down

Question 3

Lift

Answer 3

The upward force produced by airflow over
the wings.

Question 4

Thrust

Answer 4

The forward
component of flight.

Question 5

Lift explained

Answer 5

A bird’s wing is shaped so that it acts as
an airfoil (also described as cambered), a
curved surface that provides lift and
reduces drag.
Air flows faster over the upper surface of the wing
compared to the lower surface of the wing. The
faster flow of air over the upperwing results in lower
pressure against the upperwing compared to the
underwing, which leads to lift. This is called the
Bernoulli effect.
In addition, the curved underside of the
wing deflects air downward. This also
contributes to overall lift.
* The amount of lift produced increases with
airspeed and with the wing area.
The angle of attack, which is
the orientation of the wing with
respect to a current of air, also
affects lift.

Question 6

Thrust explained

Answer 6

Because lift is perpendicular to the direction of
airflow over the wing, birds can manipulate the
shape and direction of their cambered wings
during flapping to change the direction or
orientation of lift. By rotating the upper surface of
the wing downward/forward during the
downstroke of a wing flap, the direction of the lift
force will also be rotated forward. The net
forward component of this altered lift is called
thrust. (See Figure 5-1c, Slide #4.)

Question 7

Soaring Flight

Answer 7

• Soaring is flying without flapping.
• Birds who are gliding will gradually lose
  altitude due to drag.
• However, birds can take advantage of
  moving air to overcome that drag.
• Two types of soaring: thermal soaring and
  dynamic soaring.

Question 8

Thermal Soaring

Answer 8

using hot air to rise

Question 9

Dynamic Soaring

Answer 9

Ocean up down motion

Question 10

Flapping Flight

Answer 10

Flapping flight
introduces much more
thrust.
* As stated previously,
birds create thrust on
the downward stroke by
rotating the angle of
attack downward,
thereby producing a
forward component.

Question 11

The Alula

Answer 11

The alula is the feathered first digit of the hand.

It can be used to control air flow over the top of the wing to maintain lift and prevent stalling at slow speeds or high angles of attack.

Extending the alula creates a slot at the leading edge of the wing that keeps airflow close to the wing and reduces turbulence; this helps especially during landing and takeoff.

Question 12

Hummingbird Flight

Answer 12

Hummingbirds can create lift and thrust on both the downstroke and the upstroke.

• Hummingbirds flap their wings up to 78 times per minute.

Question 13

Wing Sizes and Shapes

Answer 13

The energetic costs of flight are determined in part by the relationship between the wing area and the bird’s body mass. This relationship is
called wing loading.

Question 14

Aspect ratio is defined as

Answer 14

the square of the wingspan divided by the total wing area

Question 15

Wings with a high aspect ratio are ___, while those with a low aspect ratio are _____.

Birds that fly at high speeds have wings with a ____ aspect ratio.

Answer 15

pointed, wide and rounded, high

Question 16

Ducks have short, ____-aspect-ratio wings and ___ wing
loadings, which allows for rapid flight, but also requires
some running on the water’s surface during takeoff.

Answer 16

high, high

Question 17

Thermal soarers tend to have wings with a ____ aspect
ratio.

Answer 17

low

Question 18

Dynamic soarers ten to have a ___ aspect ratio and ___ wing loading.

Answer 18

high, low

Question 19

Grouse have ___ aspect ratios and ___ wing loadings;
they usually only fly for short distances.

Answer 19

low, high,

Question 20

Modifications to the Skeleton

Answer 20

Fusion and reinforcement makes the skeleton both
powerful and delicate.
* Hollow bones are filled with struts.
* Lightweight, toothless bill.
* Uncinate process on ribs reinforce the rib cage.
* The keel on the sternum allows for attachment of flight
muscles.
* The coracoid, scapula, and furcula form a triangular
structure that helps to resist the pressures created by
wingstrokes.
* The hand bones are fused into the carpometacarpus for
additional strength.

Question 21

Flight muscles

Answer 21

The main flight muscles are the pectoralis and
the supracoracoideus.
* The pectoralis attaches on one end to the keel
and to the furcula and on the other end to the
humerus. Contraction pulls the wings downward.
* The supracoracoideus attaches to the keel and
to the top side of the humerus through a tendon
that passes upward and around the triosseal
canals (located where the coracoid, scapula,
and furcula come together). Contraction pulls
the wings upward like a pulley.

Question 22

“Flight” in Penguins

Answer 22

The forelimbs of
penguins have been
modified to be used as
paddles. The bones are
thicker, stronger, and
heavier. The elbow and
wrist joints are not
flexible.