Following Illegal Hunters Who Illegally Snare the Nation's Endangered Singing Birds.

The conservationist's vision darts over miles of dense fields, looking for suspicious activity in the pre-dawn darkness.

He utters less than a whisper as the team seeks a concealed position in the open area. In the distance, the sprawling city of Beijing has yet to wake. As we wait, the only sound is the sound of breathing.

And then, as the sky turns a shade lighter with the approaching day, there is the crunch of footsteps. The hunters have arrived.

Trapped

Overhead, billions of birds, many so small that they could rest in the cup of a hand, are traveling to the south for winter.

They have taken advantage of the long summer days in Siberia, or Mongolia, feasting on insects and fruit. As the year winds down and icy winds bring the early cold of winter, they journey to warmer places to breed and eat.

The nation hosts more than 1,500 bird species, representing roughly 13% of the global population – more than 800 of those are migratory birds. Several of the major migration routes they follow cross through China.

This particular field being monitored, on the fringes of the Chinese capital, is an haven for small birds – farther in and the urban landscape offer little opportunity to rest among towering rows of concrete.

It is also an oasis for the poachers and their "barely visible nets", so fine you can almost miss them.

The one we nearly walked into was extending over a large section of the field and propped up with bamboo poles. At its center, a small finch was fighting hard to untangle itself, but the more it moved, the more its feet got ensnared.

It was a protected songbird, a protected bird in China, and an important "indicator species" – which signifies if its numbers are thriving, so is its environment.

Pursuing the Poachers

Silva, who is in his 30s, does this work for free using his personal funds. He has given up on many nights of sleep to set songbirds free, and he has spent the last decade convincing the police in Beijing to prioritize this issue.

"Initially, no-one cared," he says.

So he enlisted helpers who did care and established a group known as the Bird Protection Unit. He organized public meetings and brought in the officials of the relevant authorities. These consistent and determined acts of persuasion seem to have paid off. The police realized that catching poachers also helped in tracking down other kinds of criminal activity.

"We found our objectives became somewhat shared," Silva says, noting that enforcement is still patchy.

His passion for avian life began during childhood. He was raised in the nineties in a much changed capital.

He recalls roaming through the fields on the city's edges where he discovered birds, frogs and snakes. "However, beginning in the 2000s, everything changed."

China's booming economy brought a huge influx of rural workers to cities. This fast-paced development meant grasslands were seen as empty places to build, not sanctuaries to conserve.

The transformation was alarming. The grasslands began to shrink, as did the ecosystems they sustained.

"I decided back then to dedicate myself to preservation and I took this path," he says.

It has not been an easy life. A major Beijing's biggest bird dealers discovered he was under scrutiny by Silva and retaliated.

"He gathered several of his accomplices who surrounded me and assaulted me," Silva recalls. He says he went to the police but those responsible were not held accountable.

He has also seen the departure of his team of helpers over the years. This work demands stealth and sleepless nights. Silva says few people are willing to take on the difficult – and sometimes dangerous job.

"I do this full-time," he says. "I made it a project because if you want to tackle this challenge, you must give it your all. You can't do it part-time."

He says donations pays for some of the costs – over 100,000 yuan a year – but support has waned because of the slowing economy.

So he has developed new ways to hunt the hunters.

He examines satellite imagery to find the paths created by the poachers. He maps those against the birds' flight paths and looks for areas where they may rest. The aerial views can even show lines of net traps which can catch hundreds of small birds during darkness.

"Siberian rubythroats and bluethroats command a high price," Silva says. "In big cities like Beijing and Tianjin, those who want to keep birds are now quite wealthy."

While there are environmental regulations in place, Silva argues the penalties to deter the activity do not exceed the financial benefits of trapping and trading songbirds.

Keeping a caged bird was – and for some people in China, still is – a status symbol. This originates from the imperial era. Nobles and elites would build ornate bamboo cages to display their birds.

It's a tradition that persists mainly among older individuals in their later years. Silva says some elderly citizens may not understand they are breaking the law, or understand that so many more birds had to die in a trap for them to purchase a pet.

"These individuals often lacked enough to eat in their youth. Now with a little money, they have inherited the habit and custom of keeping birds in cages," he says. "China developed so fast, there was little opportunity to educate people about ecology. Once adults' values are formed, they're extremely difficult to change."

Busted

Along a riverside path in Beijing, a vendor has several tiny enclosures with tiny twittering birds.

A separate individual stands outside a local market holding a bird cage shrouded in a black veil. He tells passers-by quietly that his songbird is rare, worth nearly 1900 yuan.

This is a glimpse of an traditional side of the city where small unofficial traders have created their own market.

The path by the river extends over several miles and on a sunny weekday morning, there were people looking at everything from vintage jewellery to dentures.

We were told that wild songbirds could be bought in a small park. The location was not concealed.

Loud music played from a speaker in a shaded area where a troop of elderly ladies were performing a traditional dance. Nearby several men, all over 50, had congregated with bird cages – some had multiple in their hands. Most were covered in black fabric.

But on this occasion there would be no transactions because the police had appeared. They were interviewing the bird owners and taking names. Unyielding, one man said he was {taking his caged bird for a walk|simply exercising his