| Of all the
Arctic’s creatures, birds undertake the most dramatic autumn
migration. Swarms of birds native to the temperate and the arctic zones seek warmer
regions late in the summer and autumn returning to their original nesting sites in the
spring. Such seasonal migrations
also occur among mammals, such as caribou who move from the tundra to the forests, and the Greenland seal (Pagophilus
groenlandicus) that makes a long journey from Greenland to Spitsbergen and Jan
Mayn islands, where their young are born.
Many fish migrate from
open water out at sea to warmer coastal waters and from the north to warmer southern
regions during the winter months.
There are many theories trying to
explain the origin of migrations and the physiological mechanisms that guide animals in
migratory journeys. However, biologists have not all agreed on one specific theory.
The seasonal movements of birds and
most other migrating animals happen because of both inside and outside stimuli that
release a physiological migratory "trigger". Once an animal has begun a
migratory journey, however, many factors act to keep it on the right path
Navigation by the sun
or the stars seem to be involved in the migration of birds,
and fish may be guided through the sea by minute traces of chemical odors from their
ancestral rivers. Some scientist believe birds may be using the magnetic field of the
Earth and are effected by its rotation around an axis. These two forces are different
depending on where you are on Earth and maybe that is what directs the birds when flying!!
One of the coolest
"migrators" is The Arctic tern.
Every fall it heads eastward across
the Atlantic and down the west coast of Europe and Africa to winter in the Antarctic
Ocean...Yes, by the South Pole!! In spring they return all the way north, following the
East Coast of South and North America, a round trip that can total 22,000 miles (35,000
km). They see more daylight than any other living creature since they are in both the
Arctic and Antarctic during the periods of the longest days. |