(wind blowing) (pencil scratching) - [Narrator] The highest chute in the Andes was the Quelccaya glacier in Peru, at 5,700 meters.

The crew are hoping to catch the first images of birds nesting inside a glacier.

(horses neighing) - We are packing up to go to the ice cap, at last.

We're heading to Quelccaya after a week of acclimatizing to the altitude.

We've got to hike about five hours, and then we should be there.

So, it's exciting, and slightly scary at the same time 'cause we don't quite know what we're gonna find when we get there.

- [Narrator] Ahead of the crew, a team of scientists is already at the glacier looking for nests.

- [Man] Oh, I'm out of breath already.

(thunder rumbles) - [Narrator] At this altitude, there is only half the oxygen compared to sea level.

- I think I left my lungs down there.

- We're checking our pulses quite often.

And our oxygen levels, just to sort of make sure we're not clinically dead.

193.

- 215.

- [Matthew] That can't be right.

- [Narrator] With blood oxygen levels dangerously low, glacier camp is a welcome sight.

This trip has been nine months in the planning, and the crew still don't know if the science team has found any nests.

- Good to have everybody together.

- Yeah.

- [Matthew] So, you gotta ask.

What's the news?

- We found fledglings.

We found one nest building.

- Yay!

- One with chicks.

- Well, I don't know about you, but my heart rate's just gone up just a bit more.

- [Pete] Yeah, yeah.

- [Matthew] It's very exciting.

- [Narrator] With the promise of something to film, the crew settle into camp, and prepare to spend their first oxygen-starved night in temperatures down to minus 10.

- It's half past seven.

We're freezing cold.

I have to brush my teeth before the water freezes.

Try not to spit in the vicinity of Pete's strange tent contraption.

- Goodnight.

- [Man] Goodnight, Pete.

- [Matthew] Sweet dreams.

- It's about half five, six.

Just woken up after a night of not really sleeping at all.

You are kind of out of breath the whole night, as if you've just been doing loads of exercises.

- [Narrator] But the real effort is just beginning.

As the team hike to Quelccaya.

The parent birds aren't around.

Ice climber, Cokey, has less than an hour to install a nest camera before they return from feeding in the valley below.

- It's quite hard to watch.

It just looks so precarious.

- [Narrator] The glacier's melting fast and is unstable.

- I'll be pleased when he's down.

Let's just put it that way.

- [Narrator] Back on the ground, wires from the camera are connected to a filming hide.

- So, this is the moment of truth.

Everything should be plugged in, ready to go.

- Oh.

- And there we have a view into a glacier bird's nest.

Look at that.

So, you can see here.

You can see the little bit of fluff on the two chicks.

Brilliant, we've got a window into their little intimate lives when the parents come in to feed them, see how the chicks grow.

What a privileged little view we've got.

- [Narrator] This is the first ever footage of a glacier bird nest.

But there is a chance the adults won't accept the camera.

(birds tweeting) If they're too weary to enter the nest, the mission will have to be abandoned.

- They just flew up, so they're 20-25 meters.

But they're getting closer.

- Okay, so I can see the birds.

He's about three or four meters up to the right of the nest.

He's checking it out.

It's a new feature in their environment.

- Come on, be brave.

- [Matthew] (whispering) Yes, she's in there, she's in there.

- [Pete] Now, it's feeding.

- [Matthew] Yeah.

- Flying out now.

- Oh, right passed the camera.

- [Narrator] With the birds accepting the camera, the hope is that the team will now discover exactly what goes on in the hidden nest.

- Before this visit, all that was known about the nesting of this species was from two nests found the end of April 2014.

This activity is, previously, undocumented.

It will help to build the story of why and when the birds are nesting on the ice.

- [Narrator] Spencer was part of the original team that discovered the birds unique behavior.

His search for new nests even takes him underneath the glacier.

- [Spencer] A little nerve-racking being under here with a lot of ice over me that I know is melting, and actively moving.

If it starts to creak, run.

- [Narrator] Science runs in Spencer's family.

His father, Doug, has been studying Quelccaya for years.

Since 1980, the glacier has shrunk by around a third.

- Whether Quelccaya's here in 20 years, 50 years, or 100 years, it's pretty difficult to speculate.

Especially, given the increasing rate at which we're changing the atmosphere.

It's a little bit of a race against time trying to salvage and understand what's going on in these ice caps while they're still here.

- [Narrator] Back in the hide, there is some good news.

- So, after a week of waiting, we've finally seen on of the chicks fledge.

Which is very exciting.

And now, there's one chick left, looking a bit sad.

It's alone for the first time in its life, probably doesn't know what's going on.

And we're hoping the parents can encourage it to fledge soon.

- [Narrator] The chick's home will not last much longer.

- C'mon, little fella.

- It's like it's not really quite ready to take the plunge.

- Coming up.

Coming up to yours Murphy.

- [Murphy] Ready.

- [Matthew] Oh, he's popped back in his nest.

(laughs) He's just not up for it.

Oh, chick's flying, chick's flying.

(birds tweeting) - So, we've really been watching them, and you've seen the snow melting away little by little around their nest.

Then, one day the nest is gonna fall and slide down this cliff face, and luckily, they've managed to fledge before that happened.

So, yeah, good luck to them in this really harsh environment.

Which is too harsh for me.

I'm gonna go down the mountain and get some oxygen.

(soft music)