You also travel with a flock of migrating birds.

你还随着一群徙的鸟到处旅行。

These are migrations that have been compared to migrations on the Serengeti in Africa.

“这些徙可与非洲塞伦盖蒂平原上的大徙相提并论。

It's one of nature's most spectacular mass migrations.

黑脉金斑蝶的徙是自然界最壮观的大规模徙之一。

But for many migrants-like smaller songbirds-nighttime is the right time, when it comes to migration.

但是，对于小型众多徙动物而言，夜晚才是适合徙的时间。

And why go north for the winter when most migrants move south?

当大部分的动物向南部徙过冬时他们却向北部徙？

Vertical migration in the ocean is the largest net animal movement on our planet.

海洋中的垂直徙是地球上最大的动物净徙。

And they seem to be migrating north.

它们似乎正在向北徙。

You are now ready for the great migration.

准备好开始大徙吧。

The result: a large-scale polar bear treadmill. And all that walking requires extra fuel.

大批北极熊徒步徙。而这种徙需要额外的能量。

The birds are migrating at night.

鸟儿在夜间徙。

We have the right to move freely in our own countries.

人人在各国境内有权自由徙。

Meadow-larks migrate but a very short distance.

草地云雀徙的距离很短。

Many birds will often migrate just to find food.

许多鸟类经常徙只是了寻找食物。

It is one of the largest migrations of fish in the world.

这是世界上最大的鱼类徙之一。

Mountain bongos once moved in large numbers.

山地紫羚曾经成群结队地徙。

The Coa Valley provides a migratory corridor for rare species.

科阿山谷稀有物种提供了徙通道。

The Coa Valley provides a migratory corridor for rare species.

科阿山谷稀有物种提供了徙通道。

20. Where do monarch butterflies settle at the end of the migration?

20。帝王蝶在徙的最后会安顿在哪里？

The tribe's forceful removal began in the late 19th century.

该部落的强行徙始于19世纪末。

The count down to their autumn migration has already begun.

秋季的徙已经开始了倒计时。