The four low walls of the concrete competition ring are surrounded by young men, yelling in Bahasa.

It's like a boxing match, but this competition is quite different — the competitors, 60 of them, hang high from the roof. And they're not fighting; they're singing.

This is a songbird competition in Pontianak, the capital of Indonesia's West Kalimantan province.

Black-and-white oriental magpie-robins hang from the roof, singing for several minutes without stopping.

They sit in beautifully carved, ornate birdcages that are ordinarily found on verandahs, street corners, backyards, and shopfronts.

Songbird competitions are big business in Indonesia. ( ABC RN: Gretchen Miller )

On any given week in Indonesia, there are thousands of songbird competitions like this throughout its many districts.

They're filled with birds illegally caught in forests by trappers — and the demand for songbirds is growing.

A recent Planet Indonesia survey found over 25,000 songbirds were being sold in markets just in the Kalimantan area. Wildlife trade monitoring network, TRAFFIC, found 19,000 birds for sale in just three days in Jakarta in 2016.

Big business, big impact

While songbird competitions continue to rise in popularity across Indonesia, the sport is endangering already threatened species.

In 2016, TRAFFIC's study found 19 species of Indonesian songbirds were endangered because of the trade.

There are over 90 listings of protected birds in Indonesia — some of those include individual species, and some include entire families.

Songbird competitions are big business. Largely a male "sport", people from all economic groups compete and spend their money on accessories.

Songbird winners can fetch up to 30 times the average monthly income of Indonesians. ( Getty Images: Goh Chai Hin )

"It's all about prestige, you know," says Novia Sagita, the co-director of Planet Indonesia, an NGO set up to address the songbird crisis by working directly with villages.

Fellow co-director Adam Miller says the trade involves almost 300 species, and one to two million birds are traded every year in Indonesia.

"It's continually growing and growing," he said. "There's more bird clubs popping up, there's more species involved in the competition. These men are very excited about their birds."

While the prize money is often meagre, the value of the bird can go up dramatically on the basis of a win.

One smiling winner said his bird, which he first bought for $US10, was now worth $US6,000. Winners can fetch up to $20,000, or 30 times the average monthly income of Indonesians.

Originally a Javanese tradition, songbird competitions are popular across Indonesia. ( Getty Images: Dirk Lehmhus/ EyeEm )

Pressure on forests

These songbird competitions gained momentum in the mid-1970s, when a Javanese non-government organisation decided to push the tradition of keeping songbirds as a hobby and even encouraged competitions.

That push was combined with President Suharto's transmigration program, which peaked during the early 1980s.

It meant freedom of movement around Indonesia, but also that Javanese traditions like songbird keeping spread around the country.

Now, the pressure on the forests is immense. Crazes for particular species see them wiped out in the wild.

Over a few years a bird can go from being ranked "common" to "vulnerable", as did the greater green leafbird — now found more in bird markets than in the forests.

One village at a time

Bird trappers are often locals hoping to make a bit of money on the side. It's a cash flow issue, so Planet Indonesia's Ms Sagita works closely with communities to help them improve their economics.

This includes providing literacy programs, or helping Indonesians breed animals as a business.

"We'll do it together and we call it our community business system," said Ms Sagita, who teaches locals everything from bookkeeping to management skills.

The process is beginning to work, but changing cultural traditions one village at a time is not a quick process.

Meanwhile, breeding programs have proved challenging. Mr Miller says they are not "the solution".

"With case after case of captive breeding within Indonesia, if you visit these breeders you'll never see any chicks, or juveniles — they're just laundering species from the wild," he says.

"There is some conservation breeding going on but they've all been shut down, because every bird they release get trapped again."

Javan green magpies are just one species of songbird in Indonesia. ( Supplied: Jonathan Beilby )

While birds are likely to be caught again, education is needed for whole communities to leave a patch of forest alone.

"I don't know if the wild bird trade in Indonesia will stop in a million years, completely," Mr Miller says.

"I think it's so embedded here. What we can do over time is for certain species try to cut them out of the trade and try to set up some system of limitation.

"There has to be something in place because right now it's a free-for-all."