(wind blowing gently) (birds singing) - [Narrator] At six in the morning, the thermometer reads zero.

- [Ralph] I spent a long time looking at them, a lot of cold mornings out counting birds and looking at their habitat.

- [Narrator] We've been told this is the best time in one of the best places in the US to witness one of the great triumphs in modern wildlife recovery.

- [Ralph] Yeah, they're kinda coming out pretty high this morning.

There's about a dozen of them or more in the air.

- [Narrator] Bald eagles leave the forest where they've spent the night, but this morning, they play coy.

We and the other bird watchers only see a couple of dozen.

(Ralph laughs) - [Ralph] Yeah, if I don't see 50 or more at a time, well, I'm not impressed, so.

- [Narrator] Ralph Opp lives in the one region that attracts more bald eagles than any place else in the US, except Alaska.

The Klamath Basin of Southern Oregon lures seven to 800 eagles every winter.

(eagle chirping) Back in 1976, he was the biologist who discovered the shelter in the forest where all the eagles go every night.

He was instrumental in having that night roost set aside as the Bear Valley National Wildlife Refuge.

- We weren't aware, here anyway, that the night roosts were that important.

And fortunately, we determined, discovered that in the '70s, was able to protect it.

So it is a federal bald eagle refuge, one of the few in the country.

- [Narrator] Eagles rarely allow people to come very close.

Yet here in Southern Oregon, bird watchers can approach less than 50 yards away.

Their presence barely ruffles a feather.

(eagle chirping) - A gathering of eagles, the bald eagles, is called a convocation, and I think that's pretty appropriate.

I like that for, you know, it's a regal bird.

Yeah, they don't just have a meeting, they have a convocation.

- [Narrator] Many of these regal symbols of America are actually Canadians.

A large number fly 1,200 miles from the Northern Territories to winter in Oregon, lured here by food.

(birds squawking) Hundreds of thousands of geese, swans, cranes and ducks stop at the Klamath Marshes.

(birds squawking) - [Ralph] Something like 80% of all of the waterfowl that migrate north and south in the Pacific Flyway funnel through this area.

The eagles have learned to come here and winter in concert with them.

- [Narrator] The eagles eat well.

Dinner is served on the frozen lake, often within view of lucky survivors.

To see so many bald eagles in one spot may seem spectacular, but it's downright astonishing considering how few eagles there were 50 years ago.

- We were down to about 20 nesting pairs in the state of Oregon, you know, in the '50s and '60s.

And then on into the '70s is when we started our recovery activities for the bald eagle.

And we're back to probably seven, 800 nesting pairs in Oregon now.

A much safer, stable population for these birds.

(eagle chirps) - [Narrator] The rebound in eagle numbers can be seen across the state, including the Willamette Valley.

In one day south of Albany, we see nearly four dozen.

- In 2010, in January, we counted 171 bald eagles just in this Linn County area.

- [Interviewer] Just Linn County?

- Just Linn County.

This is probably the second largest concentration of bald eagles in the state, during the wintertime.

- [Narrator] For seven winters in a row, Jeff Fleischer has led a survey effort for the Audubon Society.

He and an army of volunteer researchers drive 146 routes around the state, counting birds of prey.

- Oh, hello!

We've got a major dining center over here.

- [Narrator] The eagles have found a dead sheep.

- [Jeff] We've got one, two, right close to the carcass.

- [Narrator] When they stalk smaller prey, winter's bare cottonwoods make for the ideal hunting perch.

- For example, the eagles back here, they know we're here.

I mean, they can see us as well as we can see them through the binoculars that we're using.

(truck whooshes) - [Narrator] Just as in Klamath, the numbers of eagles in the Willamette Valley are on the rise.

- [Jeff] In the last five years, we've gone from 40 or 50 to 170 two years ago.

(engine rumbling) (tires crunching) - [Narrator] There's one spot in Oregon where eagles have some trouble.

On the Lower Columbia, numbers are up yet many of the nests fail to hatch chicks.

- They're producing about half the number of eagles that they should produce.

And we've been trying to track down since the 1980s why that's the case.

(carabiner clicks) (rope whirs) Through!

- [Narrator] To solve the mystery of the failed nests, Jeremy Buck must go where the eagles live.

- What we do is we come in very fast.

We try to get a lineup into the tree so we can ascend up to that nest, pull one of the eggs out.

We need to get the slack out.

- [Narrator] Jeremy is a biologist with US Fish and Wildlife.

(Jeremy exhales heavily) - This is the fun part!

- [Narrator] Over 15 years of research, Jeremy has climbed into 30 eagle nests.

(eagle chirping) - [Jeremy] Gotta get through a little bit of brush here.

The Sitka spruce have a lot of branches up there.

They're actually kinda fun to climb.

You just gotta make sure you do it safely.

Oh!

(Jeremy breathing heavily) Beautiful view over the river.

(eagles chirping) Can hear the eagles wanting to get back onto their nest, which we'll let them do in a minute.

- [Narrator] More than 100 feet up, Jeremy reaches the nest.

They are large, strong, and heavy.

They can weigh up to a ton.

Sturdy enough for Jeremy to climb in if necessary.

- [Jeremy] Looks like a lot of feathers up here.

Looks like the eagles have covered up eggs with moss!

These eggs are cold, which means they've been probably cold for some time.

- [Narrator] Jeremy will take one egg.

It could contain clues about why it failed to hatch.

- [Jeremy] As long as we can move out quickly, they'll come back and they'll sit on that remaining egg.

- [Narrator] Two days later in the lab, Jeremy is ready to begin analyzing why this egg produced no chick.

- [Jeremy] 124.13.

The egg should look like a chicken egg.

When you break open a chicken egg and a bright yellow yolk comes out, that's a healthy egg.

That's what it should look like.

Ours was kind of degraded, very milky, like a rotten egg.

- [Narrator] After several years of testing eggs, they found a pattern.

The shells are too thin.

And when they test the shell itself, they find elevated levels of a toxic chemical no one thinks about anymore: DDT and its byproduct, DDE.

- [Jeremy] I was shocked at the results that DDE was still in the eggs at high concentrations.

And that thing- - [Narrator] Every egg tested since 1985 has DDT residues.

- [Jeremy] They generally come out white.

This one's quite a bit dirty.

Hard to say!

- [Narrator] The levels are higher along the Columbia than any other river system in Oregon.

Jeremy suspects the pesticide has collected in the sediments here where the river grows slow and wide.

DDT lingers, despite being banned in the US 40 years ago.

- [Jeremy] It's very persistent.

It takes a long time to break down in the environment.

- [Narrator] Despite low birth rates here, even along the Columbia, eagle numbers are healthier.

Bald eagles spent 40 years under special protection.

In 2007, federal biologists officially removed them from the Endangered Species List.

Ralph Opp was one of those biologists who insured Oregon played an important role in their recovery.

- [Ralph] Eagles are my life!

Yeah, I was lucky.

I feel real good about it.

Yeah!

We did a lot here to help get them off of the Endangered Species List.

- [Narrator] From the banks of the Columbia River to the marshes of Klamath Falls, success is in the air.

(eagle chirping) (no audio) (no audio) - Great people just doing their thing in their own Northwesty way.

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