Many birds have along the latitude season migration characteristic.when summer,
these birds reproduce in the latitude higher temperate zone area,when winter,these
birds in the latitude lower tropics area. At the end of summer and the initially of
fall time these birds toward move to the south by the reproduction transfer to cross
the winter place,but when spring is comeing, from crosses the winter north to
return to the reproduction place. These with season to migrate of the north and
south migration birds call it along with the seasonal variation "corbie"