(bright music) - [Host] The greatest bald eagle congregation on earth happens in southeastern Alaska just before the fierce Alaskan winter.

(bright music) The journey takes several hours by ferry through the ice capped glaciers of the Alaskan fjords.

- Propped up in front of us, we have a pod of Orca killer whales.

- Oh, amazing, unbelievable.

(upbeat music) (bird cawing) The village of Haines lies on a remote peninsula, nestled between the Chilkat and Chilkoot rivers.

In early November, it's home to the largest bald eagle migration in the world.

(bright music continues) So we're gonna see some bald eagles here.

- Well, there's three of them right here.

These are all adults.

And then, oh, here's some bear tracks right here.

So this is a grizzly or a brown bear.

Those are the claws.

And of course, he's here for the same reason the eagles are here.

There's all these fish.

And look, is that an eagle right there?

Yeah, that's - and so that's an eagle right there eating a fish.

(bright music plays) The congregation here is one of the great spectacles of wildlife in the world.

I mean, it's akin to what happens in the Serengeti when the wildebeest, you know, migrate.

(eagle caws) - And do you think it's appropriate that the American bald eagle is in effect a symbol of our country and our national seal?

- Yeah, I think so.

The bald eagle is unique to our country and technically we only have two eagles in North America, the golden eagle and the bald eagle.

And everybody loved the eagle.

And so, the main eagle that was chosen for a national symbol around the world, Rome and many, many other countries is the golden eagle.

The golden eagle is from the booted eagle family, the true eagles.

Those are Aquila.

And then the Haliaeetus are actually fish eagles or in the bald eagle.

- And do you think the people in the lower 48 appreciate the bald eagles and what they do for our country in terms of being a national symbol?

- In terms of a national symbol?

I think that they understand them that way.

What I don't think that they understand is the ecological value that they have.

The bald eagle is truly a symbol of the success of this ecosystem.

So there's an adult, and of course she's hunting right now.

This is observing the river and it doesn't really look like it.

She's actually watching that immature eagle eat the fish.

And she'll, at some point, if she's hungry, she'll fly over there and displace that young eagle.

And then you notice, also see that magpie.

There's a magpie stealing his share of the food too.

(bird caws) And so when they do drag a fish out, they're actually feeding a whole lot of other animals once that fish has been drug out of the the river.

- And what kind of bird is flying down there now?

- That's a gull.

- [Host] You think the gull is now gonna try to steal some of that fish?

- No, he's gonna wait his turn.

He knows better than to confront the eagle.

(dramatic music plays) - If the eagles didn't come here, what would happen to Haines, Alaska and the whole ecosystem here?

- It would start to unravel.

Most people don't realize that there's a cascade effect when eagles are gone.

You see this degradation of the ecosystem.

And in fact, the eagle is an economic value here locally because people come from all around the world to visit to see eagles here.

- But the tourists who come to Haines, Alaska is it mostly because of the bald eagles or is there other reasons they might come here?

- They come to see a pristine ecosystem intact which is a very rare thing in the world today.

(eagle caws) This ecosystem is as close to pristine as any ecosystem that exists.

In fact, this is the greatest expansive wilderness left on earth.