migration

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					Migration of the Wood Thrush
► Every  spring the Wood
 Thrush song birds take
 flight from their winter
 home in Costa Rica to
 live in their summer
 home in Maryland.
 What makes a tiny
 little bird fly thousands
 of miles year after
 year…?
First lets talk about what migration
                  is:
                  ► Migration  is the travel
                    from one place to
                    another.
                  ► Birds usually migrate
                    to find food. (not
                    because they can’t live
                    in the cold or
                    extremely hot
                    weather)
Triggers for Migration

           ►   Seasonal changes:
                Change in length of day
                 light.
                Pressure changes

           ►   Scarcity of food
           ►   Changing weather
Hours of Migration
         ► Large birds: (Hawks,
           geese, ducks, etc…)
           migrate during the
           day.
         ► Small birds like the
           Wood Thrush migrate
           at night to stay clear of
           the their larger
           preditors.
How long do they travel
            ► Most of the Birds in
              America fly to their
              winter homes in
              Mexico and Central
              America
            ► The Wood Thrush
              spends about 6 to 8
              weeks of traveling to
              Costa Rica
Are there Dangers?
         ► Migration   is very
           dangerous!
         ► Most birds fly at an
           altitude of 500 to
           2,000 feet.
         ► There are natural
           dangers (storms,
           predators) and man
           made dangers (habitat
           destruction, airplanes,
           tall buildings,…)
Are there Helpers?
         ► Birds use these clues
           to help them find their
           way:
            star patterns
            earth's magnetic field
            landscape features
             (such as mountain
             ranges, rivers,
             coastlines)
            wind patterns
So if Migration is such a big hassel
             why do it?
                  ►   Migration is a ancient
                      phenomena
                  ►   It helps keep populations
                      surviving when there is
                      inadequate food source
                      available or when a certain
                      food source is needed.
                      Example the W. Thrushes
                      Fatten up on tropical
                      berries and seeds in the
                      winter, and they feed their
                      young insects they find in
                      Maryland.
Evolutionary Benefits
           ►   Migration aids in the
               process of natural
               selection.
           ►   Natural Selection is the
               force behind evolution.
           ►   Migration ensures that the
               strongest individuals will
               live long enough to
               reproduce, therefore
               producing a new
               generation of strong birds.
                 El Fin




Hooray the Wood Thrush made it to Maryland!

				
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posted:10/25/2012
language:English
pages:12