You also travel with a flock of migrating birds.

你还随着一群迁徙鸟到处旅行。

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

“这些迁徙可与非洲塞伦盖蒂平原上大迁徙相提并论。

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

但是，对于小型鸣禽等众多迁徙动物而言，夜晚才是适合迁徙间。

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

为什么当大部分动物向南部迁徙过冬却向北部迁徙？

And they seem to be migrating north.

它似乎正在向北迁徙。

You are now ready for the great migration.

准备好开始大迁徙吧。

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

大批北极熊徒步迁徙。而这种迁徙需要额外能量。

The Coa Valley provides a migratory corridor for rare species.

科阿山谷为稀有物种提供了迁徙通道。

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

人人在各国境内有权自由迁徙。

The birds are migrating at night.

鸟儿在夜间迁徙。

It also tells us that these were migrating dinosaurs.

这也说明它是迁徙恐龙。

Now there's a whole host of reasons why birds may choose to migrate at night.

鸟儿选择夜间迁徙有很多原因。

Many birds will often migrate just to find food.

许多鸟类经常迁徙只是为了寻找食物。

Mountain bongos once moved in large numbers.

山地紫羚曾经成群结队地迁徙。

We could see migration at a continental scale.

我可以看到大陆范围内迁徙。

Some birds migrate to find warmer weather.

有些鸟迁徙以寻找更温暖气候。

The Coa Valley provides a migratory corridor for rare species.

科阿山谷为稀有物种提供了迁徙通道。

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

该部落强行迁徙始于19世纪末。

The count down to their autumn migration has already begun.

秋季迁徙已经开始了倒计。

It turns out that 80 percent of them migrate at night.

其中 80% 都在夜间迁徙。