Page 104 - The Origin of Birds and Flight

In analyzing the complex structure of bird feathers, Nic Bishop says this
in his book The Secrets of Animal Flight:
Feathers may look simple, but they’re really very complicated. Each one
can have more than a million tiny parts. 1
Feathers’ complex anatomy varies according to their function. For
example, flight feathers’ complex shapes result from small wings, resem-
bling fabric, that extend towards both sides. This stem is strong yet hollow,
and the extensions on it—known as hooks—have a strong but flexible
structure. 2
The barbules on the feather have to be strong, yet flexible enough not to
snap in the wind. Thanks to this special creation, birds can make better use
of air currents than the best gliders ever designed by engineers. Were it not
for the tiny hooks in their feathers, birds would be unable to fly at all. These
hooks prevent wind damage to the feathers by separating from one anoth-
er under certain circumstances. However, they can easily combine again
when the bird grooms itself with its beak.
Roger Tory Peterson, an expert author on ornithology, says this:
The feather is a marvel of natural engineering. It is at once extremely
light and structurally strong, much more versatile than stretched skin on
which a bat supports itself in flight, or the rigid structure of an aircraft’s
wings—and far more readily repaired or replaced when damaged . . .
Though nearly weightless, it has strength. The stiff shaft of the quill pro-
vides rigidity when support is needed, yet it is supple towards its tip,
when flexibility is required for split-second aerial maneuvering. Feel the
sleekness of the web, soft yet firm. Separate the barbs; zipper them
together again by running them through the fingertips as a bird would
preen with its bill. The intricacy of the design that allows this can be
appreciated by putting the feather under microscope. 3
Feathers have been specially created to permit the bird to fly by caus-
ing the air on their upper surface to flow faster than on the lower. Air pres-
sure on the wing is thus reduced, via what is known as the Bernoulli effect.
The top surfaces of a plane’s wings are, similarly, more angled than the
undersides. In this way, air flows more quickly over the top surface, reduc-
ing the air pressure there. Since the pressure on the underside of the wing