Page 148 - Wonderful Creatures: Children! Have You Ever Thought ?

WONDERFUL CREATURES

how unlocked, it is enough for the

bird to shake itself or to put its feat-
hers in order with its beak, to

make the feathers return to
their previous state.

In order to survive,

birds must always
keep their feathers clean,

neat and ready for use. For the care of their
feathers, they use oil sacs at the bottom of their tails. They take

some oil with their beak, and then clean and polish their feathers.
In swimming birds, this oil prevents water from reaching their skin

when they are in the water or in the rain.

In addition, birds can prevent loss of body heat by ruffling their

feathers in cold weather. In hot weather, on the other hand, they
keep their body cool by smoothing their feathers.

Each group of feathers in a particular part of the body has particu-

lar functions. For example the down feathers and the feathers that
lie along the wings and tail have different structures. Large tail feat-

hers are used for steering as well as for braking. As the wing feat-
hers are spread wide while flying, the surface area is expanded and

lift force increased. When the bird flaps its wing downwards, these
feathers come closer and prevent air passing through. As the wings

move up, the feathers open wide and permit air to pass through
them. In order to maintain their ability to fly, birds shed their feat-

hers at certain times of the year. Large torn or worn out feathers

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