Page 50 - Design in Nature

48 DESIGN IN NATURE

FEATURES OF THE FLYING MACHINES
A close examination of birds reveals that they are designed specifically
for flying. The body has been created with air-sacs and hollow bones in
order to reduce body mass and overall weight. The fluid nature of their
wastes ensures that excess water in the body is disposed of. Feathers are
extremely light structures in comparison to their volume.
Let us examine these special structures of birds one by one:
1- The skeleton
The strength of a bird's skeleton is more than adequate even though the
bones are hollow. For example, a hawfinch 7 inches long (18 cm) exerts about
151 lbs. (68.5 kg) pressure in order to crack open an olive seed. Better
"organised" than land animals, the shoulder, hip and chest bones of birds are

Longitudinal Supporting bars
cross section of The body of a bird is covered with feathers.
Wing feathers open and close as the bird flaps
a bone
its wings.
The feathers at the tips of the
Cavities wings are raised when speed
is reduced. Air passes over
the feathers and bird regains
the force to avoid falling.

Wing of an
Hollow aeroplane
bone

Wing
Supporting
bars Feathers

Cavities

The bases of the feathers
are attached to the long
wing bones.

Bird bones are extremely light but sturdy, largely because they are hollow. There is air
inside the cavities where supporting bars stiffen the bones. These hollow bones are the
main inspirations for the design of modern aeroplane wings.