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To migrate means
to move from one place to another in search of food or a warmer
climate. Raptors will migrate to a warmer place in the
fall when their prey is hibernating or has moved to a warmer
place. In the spring the raptors will migrate back to lay
their eggs and raise their families. If the raptor has
enough food and the climate is fine, they will stay where they
are and not migrate.
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There are many different migration routes that are
called ‘flyways’. As they migrate, the birds start to get tired. This is because they
have a long way to go! How would you feel running a marathon
over and over again? Exhausted, right? This is why birds of
prey usually need some help to get where they are going.
One way they can save energy is from "riding" updrafts
that come from cold fronts. (See the top diagram to the
right.)
Updrafts push air up,
making a current of air that raptors ride on, saving
them energy so that they can go longer distances.
Updrafts are formed by very strong winds hitting
mountain ridges. The air currents follow the shape
of the mountain, rising until it goes up and over the
mountain.
Another way the raptors save energy is by riding thermals.
Thermals are created by the sun heating up the ground and air
close to the ground in open areas such as fields. (See
bottom right diagram.) The heated
air rises up creating something like an elevator for the
raptors. They ride the thermals up and up, and then at the peak
they soar off in their intended direction.
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Each raptor generally migrates at the same time each
year. For example, most
Broad-winged Hawks migrate in the middle of September.
Mostly all the raptors migrate sometime between mid-September and the end
of November.
During migration it can be very dangerous for raptors.
Many of them die because of starvation, thirst, and
exhaustion. Also, getting lost and being eaten are
other threats to migrating raptors.
A question that many people have asked is “How do the
birds know their way to their final destination?”
Raptors know their way because of the position of the
sun in the sky. Also, they sometimes fly along
mountain ridges and coastlines until they reach where
they are going. They rarely fly over large bodies of
water because there are no thermals.
The magnetic fields in the ground may be used for some
raptors as a sort of a compass. Night fliers like
owls sometimes use the moon and stars to decide where to
go.
Sometimes raptors may migrate thousands of miles. For
example,
Swainson’s Hawks migrate 7,000 miles in their trip to a
warmer climate. Raptors know when to migrate when they can’t
find any food, and when they notice the days are getting
shorter! |
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Works Cited:
Green, Jen. Birds. Milwaukee: Gareth Stevens,
1998.
Migration of Birds of Prey. 18 Mar. 2008.
<http://hawkmountain.org/media/speciesinfo.pdf>.
National Audubon Society. First Field Guide Birds.
New York: Chanticleer Press, Inc., 1998. |