migration造句

Swallows begin their migration south in autumn.
燕子在秋季开始向南方迁移.

Change of climate must have had a powerful influence on migration.
气候的变化对于迁移必曾有过极大的影响.

Certain other factors are also involved at the secondary - migration stage.
在二次运移中也包括其他一些因素.

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