The activist's vision darts over vast expanses of tall grassland, looking for any movement in the inky blackness.
He utters less than a whisper as they attempt to locate a concealed position in the open area. In the distance, the sprawling city of Beijing remains asleep. As we wait, the only sound is the sound of breathing.
And then, as the sky turns a shade lighter ahead of sunrise, the sound of footsteps emerges. The hunters have arrived.
Overhead, countless migratory birds, many so small that they could rest in the palm of your hand, are migrating south for winter.
They have utilized the extended daylight in Siberia, or Mongolia, feasting on insects and fruit. As the year nears its end and chilling gusts bring the early cold of winter, they journey to more temperate climates to nest and feed.
China is home to 1500-plus bird species, representing roughly thirteen percent of the planet's species – more than 800 of those are birds that migrate. Several of the major migration routes they follow cross through China.
The patch of grassland being monitored, on the fringes of the Chinese capital, is an oasis for small birds – any further and the urban landscape offer little opportunity to rest among clusters of concrete.
It is equally attractive for the poachers and their "mist nets", so fine you can hardly spot them.
The trap we stumbled upon was stretched across a large section of the field and held up with bamboo poles. At its center, a meadow pipit was desperately trying to free his legs, but the more it struggled, the more its claws became tangled.
This was a meadow pipit, a species under protection in China, and an important "bio-indicator" – that means if its numbers are thriving, so is its environment.
The conservationist, in his thirties, carries out this mission for free using his own savings. He has sacrificed many sleeping hours to rescue birds, and he has spent the last 10 years urging the police in Beijing to take this crime seriously.
"In the early days, no-one cared," he says.
So he gathered a team who were concerned and launched a group called the Beijing Migratory Bird Squad. He organized community gatherings and brought in the heads of the relevant authorities. These small and persistent acts of advocacy seem to have paid off. The police realized that apprehending illegal hunters also helped in identifying other kinds of illegal operations.
"We found our objectives became partially aligned," Silva says, while pointing out that implementation remains inconsistent.
His passion for avian life began during childhood. He grew up in the 1990s in a much changed capital.
He recalls roaming through the fields on the city's edges where he discovered birds, frogs and snakes. "But starting from the 2000s, the transformation was dramatic."
Rapid economic growth brought a huge influx of rural workers to cities. This expansion meant grasslands were viewed as land for construction, not sanctuaries to conserve.
This shift shocked him. The grasslands began to shrink, as did the habitats they supported.
"I made the choice back then to work in conservation and I chose this direction," he says.
This has not made for an easy life. One of Beijing's biggest bird dealers discovered he was under scrutiny by Silva and retaliated.
"He assembled several of his associates who surrounded me and assaulted me," Silva remembers. He says he reported to the police but those responsible were not held accountable.
He has also lost his army of volunteers over the years. This work requires covert operations and lost sleep. Silva says few people are willing to take on the challenging and occasionally risky job.
"This is my full-time commitment," he says. "I made it a project because if you want to address this major issue, you must give it your all. You cannot be half-hearted."
He says donations covers 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 analyzes satellite imagery to find the routes worn away by the poachers. He maps those against the birds' migratory routes and looks for areas where they may stop for the night. The aerial views can even show netting setups which can catch hundreds of small birds during darkness.
"Certain prized species sell for a high price," Silva says. "In big cities like Beijing and Tianjin, those who want to own songbirds are now quite wealthy."
Although there are environmental regulations in place, Silva reckons the penalties to deter the activity do not outweigh the potential profits of trapping and trading songbirds.
Owning a pet bird was – and for some people in China, still is – a mark of prestige. This dates back to the Qing dynasty. Wealthy individuals would build elaborate bamboo cages to display their birds.
This custom that persists mainly among older individuals in their 60s or 70s. Silva says some elderly citizens don't realise they are committing a wildlife crime, or grasp that so many more birds were killed in a trap for them to purchase a caged bird.
"This generation didn't even have enough to eat growing up. Now with some disposable income, they have inherited the practice of caging birds," he says. "The nation progressed so fast, there was no time to raise awareness about ecology. Once people's attitudes are formed, they're really hard to change."
Along a riverside path in Beijing, a trader has several small cages with tiny twittering birds.
Another man stands outside a nearby market holding a bird cage covered by a black veil. He informs passers-by quietly that his songbird is rare, worth about 1900 yuan.
This offers a view of an old Beijing where small unofficial traders have established a niche trade.
The path by the river extends over several miles and on a sunny weekday morning, there were shoppers browsing everything from old trinkets to dentures.
We were told that protected birds could be purchased in a small park. It was easy to find.
Music was blasting from a speaker in a shaded area where a group of elderly ladies were choreographing a traditional dance. Close by several men, all in their later years, had congregated with bird cages – some had two or three in their hands. Most were concealed by dark cloth.
But today there would be no sales because the police had appeared. They were interviewing the bird owners and taking names. Defiant, one man claimed he was {taking his caged bird for a walk|simply exercising his
