季候鸟每年信守不渝地从南向北和从北向南大举迁移,是自然界一种有趣的天然现象。 鸟类不能如其他动物般在冬季冬眠,而为了不在严冬时被冻死或饿死,它们只好南飞至其他热带及温带国家。 在平时,鸟类通常是属于无群性的,但在迁徙期间,则大都成群结队,形成一个团队。 Migratory birds year after year from south to north and from north to south mass migration, nature is a kind of interesting natural phenomenon. Birds can not sleep in winter as other animals, and in order not to be frozen or starved to death in the harsh winter, they have to fly south to other tropical and temperate countries. In normal times, birds are usually unclassified, but during the migration, most of them are in droves to form a team.