There really won't be any life left for those who fall. It's all rocks.

They're looking for a rare nest made of bird saliva that's found inside caves across Southeast Asia.

In the Philippines, the harvesters are known as busyador.

I'm Alvin Villarendo. I'm a busyador of Pangalan and Nabat Island.

For centuries, Alvin Villarendo's family have put their lives on the line to gather swiftlet nests.

Just 2 pounds is worth $2,900 and it's used to make a soup that locals believe is good for your health.

Demand is so high that swiftlet farms are popping up all over Southeast Asia.

But busyadors continue to gather nests in the wild, even with the danger involved.

Alvin: Just a small mistake, it's over. You'll go straight dowm. You'll fall.

We followed Alvin on his hunt to find out why this ancient method of harvesting is still happening, and what makes this such a risky business.

Alvin and his crew gather at Bengal point on Maytiguid island.

His group consists of relatives, cousins, brothers, uncles and nephews.

They packed the boat with essential tools.flashlight

Rope, flashlight, bamboo for hooking the nest.

And they're heading to Nab that island.

It's one of the 7000 islands that make up the Philippines and it can only be reached by boat.

They get off the boat and walk barefoot across the slippery and sharp rocks.

They make the ladder as they're climbing up, they tighten the bamboo with rope.

Then they attach a piece of wood called to the ladder.

But suppose the, the stakes are high.

The but advanced bush adores like him sometimes use little to no support, only their hands and feet.

This is the most dangerous way to climb in the regional language.

It's known as a gang, gang gang or like a crab.

Alvin has had some close calls and he dislocated his shoulder ones.

That island is completely remote.

If there's an emergency, there's no way to quickly get help.

The bush adores only harvest during the day when the birds are out finding food.

Sometimes the caves are lower and easier to reach, but the waves crashing against the cliffs present a threat.

Yeah, the entrances are small but the caves are usually spacious.

They use flashlights to light the bath after spotting the nests.

Alvin uses a spray bottle filled with water to loosen them there then gently peeled away from the cave walls.

16 C partner again, the birds like the caves because Alvin and his group are also careful not to pick any nests with eggs.

He knows that if the bird survives, so will his livelihood.

Sometimes the nests are hard to reach.

The bird makes a new nest in 15 days when the old ones gone.

But sometimes all that hard work the bushido is put in is for nothing.

If the hall is no good.

Alvin and his relatives are the only people who harvest rabbit island.

That's because his ancestors discovered the caves hundreds of years ago.

Alvin himself was only nine years old when he went to the caves for the first time with his father who was also a luchador.

They spend the night on the island, but even then they're on high alert swift that nests are only harvested from December to April.

And Alvin can find as many as 2500 in those five months.

After harvesting the bush adores, clean them to remove any feathers or branches, then they divide them by their hardness and color.

Class.

A nests are the most profitable.

They're typically white, dry and made of pure saliva.

Class B nests are not as white and may have some debris mixed in and class C nests are soft and yellow.

Just £2 of the best kind are worth about $2900.

The local city hall buys the nest from the bush adores at a regulated price and sells them to private customers around the world.

The Bush Adore split the profits.

Alvin makes about $600.

Once the season is complete, it isn't a lot of money, but he says it's enough.

Okay.

The nests are made from the hardened saliva of the swift lead bird.

They are the main ingredient in bird's nest soup.

A delicacy in China and around the world, A bowl can cost as much as $100.

But today Alvin gave in and tried some in recent years, demand for the nests and bird's nest soup has gone up.

The industry is worth $5 billion and many Southeast Asian countries have turned to swiftly farming.

They have set up structures that mimic the bird's natural habitat, dark abandoned buildings that feel like caves and they use fake bird calls to attract the swift.

Let's Bouchard or say they have noticed a difference in the number of swift that nests left in the wild, but they're not sure if it's because of farming or other environmental factors.

The farms do pose a challenge to the bush adores livelihood but Alvin says gave nests are higher quality than farmed ones.

Locals believe they have medicinal properties And there's some signs that backs it up.

A 2015 study shows the nests are loaded with nutrients that can boost a child's immunity and they're rich in proteins, amino acids and vitamins that strengthen organs.

Alvin is finally home.

After two days of hunting for nests, the season is almost over for the rest of the year.

He earns a living by fishing.

His wife, Mar B is relieved for Alvin climbing the same caves.

His ancestors did is a great honor.

Now he takes pride in carrying on the tradition.