当春季来临的时候，它们又开始向北迁飞。

When spring comes, they begin their long journey north.

youdao

即使如此，飞翔肌肉的衰竭，可防止它们再次迁飞。

If so, breakdown of their flight muscles may prevent them reaching their destiny.

youdao

秋季一到，又到了鸟类飞迁的时候了。

Come autumn, it's time for the bird to prepare to migrate again.

youdao

秋季一到，又到了鸟类飞迁的时候了。

Come autumn, it's time for the bird to prepare to migrate again.

youdao