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Birds
of prey need to fly so that they can find prey. The shape of a
bird’s body allows air to easily pass over it so that they can
fly easily and not be using up huge amounts of energy.
Sometimes birds, like vultures, need to fly a really long time
before they can find their prey. Their bones don’t weigh much
because they are hollow but it still takes lots of
muscles and energy to get them up in the air and keep them
there. For example: Vultures look for dead animals and they
might fly for hours and hours before they find one. This means
that they would use a whole lot of their energy and strength to
flap their wings for that long. It takes 15 times more energy
to fly and flap as it does to just sit still.
Most birds of prey use a combination of ways to fly. They
fly by using:
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Flapping. This way uses the most energy. When they
flap down, their feathers close up and they push
against the air which makes them rise. When they
flap up, they open up their feathers to let the air
through so that they can get in the right position
to push down against the air again. |
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Gliding. The birds fly with air currents and don’t
flap their wings very much. Just like a toy glider,
they travel through the air using wind and gravity.
They will ride the wind until their weight makes
them drop lower. |
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Soaring. The birds will stay level or rise higher
by riding thermals or air currents. They don’t have
to flap their wings and that saves lots of energy.
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Riding
thermals: The sun heats up the earth and causes warm
air currents to rise. Thermals happen later in the
morning, after the sun has had time to warm up the
land. The birds will fly until they find the
thermal, and glide in circles as the warm air pushes
them up in the sky. One of our sources called it an “elevator” [Krautwurst] which
is exactly the way to imagine it. Heavy birds
like buzzards will fly to the top of one thermal
“elevator” and then go looking for another. In that way, the bird can fly
longer because he doesn’t get as tired as he would
if he flapped his wings all the time. |
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Riding updrafts: Imagine a wind current traveling through a
valley or through a city. The wind current will
hit a mountain or a building and have to go
somewhere. It follows the surface it meets and
rises along it until it reaches the top. If a
raptor flies into the current, the wind will push
him up a mountain or a building without having to
flap his wings and use energy. He can fly
longer distances if he rides updrafts and thermals. |
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Hovering. Birds can use kiting or vertical hovering
to stay in the air. |
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Kiting: If you see a bird that looks like it is flying in
one place and not moving forward in the air, it is
probably kiting. The wings are stretched out and
only very small wing flapping is done. Birds called
kites do this and others like
Red-tailed Hawks and
Rough-legged Hawks will, too. |
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Vertical hovering. This is where the bird is flying in one
place, straight up in the air, beating its wings
very quickly. Wind helps the bird stay up.
American Kestrels do this. |
Birds of prey will generally use more than
one kind of flying. A bird might use flapping, then glide up a
thermal current, and then begin flapping again. |
Works Cited:
Kalman, Bobbie. What is a bird?
New York: Crabtree, 1999. Miller,
Claire. "How birds fly." Ranger Rick. Sept.
1995. p. 25. "Monkeyshines on
health and science". Ornithology. Jun 1997. p.
10. |
