Once bird whistler Zhu Delong and fellow villagers used age-old bird-calling skills to catch birds and sell their meat. Today he helps environmentalists and bird flu researchers. Wing Tan pecks at the tale.

Zhu Delong sets up a big net trap with a pole on a beach of the East China Sea, arranges food and decoy birds and holds a long rope that can close the trap.

Everything is ready. He is about to work his once-deadly magic.

Zhu blows his bamboo whistle into the sky, first two high-pitched notes, then he moves smoothly down to a low, short tune.

"Shh. Just watch," he says, making a sign to keep quiet.

Seconds later, a small flock of black-headed birds touch down near Zhu to peck at the food he has spread out.

Then the Nanhui area man quickly pulls the rope, pulling down the pole and casting the net upon the birds.

But the 61-year-old gent - who once caught birds and killed birds for their meat - doesn't mean to harm these feathered friends he has lured with his whistle.

"I'm just checking if their feet are tagged with rings," he says as he observes his prey carefully. On their feet some wear colorful rings - their identity cards recording detailed information, such as migrating flyway, its wintering spot, when it was hatched, and so on.

Environmentalists these days pay him 2 yuan (29 US cents) per bird.

His secret weapon, the whistle, is very useful to ornithologists, environmentalists and bird flu researchers.

Zhu can imitate more than 20 bird songs, including courtship and mating calls, calls that signal food is near, calls that welcome other birds and communicate about all kinds of things, such as seasons and weather.

Seagulls, turtledoves, quail, magpie, kingfishers, geese, crows, finches and more - all answer Zhu's call.

"I can tell at first glance what kind of bird it is as it flies over my head," Zhu says proudly. "I understand their songs and they know what I'm saying with my whistle."

About 20 years ago, however, a whistle meant something very different to the birds on the beach. With this special bird-calling skill passed down from his great grandfather, this bird whistler and many others once caught birds and sold their meat as a livelihood.

"At that time, many of my fellow villagers knew how to catch sea birds with the whistle - that was how they survived," says Zhu.

Over the past 100 years since the late Qing Dynasty (1644-1911), villagers in Nanhui's Luchaogang, a small fishing town on Hangzhou Bay, have earned their living by catching sea birds.

In 1884, refugees from neighboring provinces fled to Penggongtang (today's Shuyuan Village in Luchaogang) to get away from the national famine. However, due to the serious land salinization, farming was impossible.

The clever villagers gradually learned to live on what the Mother Nature presented them, the sea. They caught fish and birds to eat.

They developed whistles and learned to imitate birds' calls, to lure them from the sky to the ground.

For generations, bird-catching has been an essential skill for locals.

During the 1950s, the remote village had more than 70 people, around 30 families, who made their living on catching sea birds.

"I learned it from my grandfather and he was taught by his grandfather. We blew the best whistles in the village," Zhu says proudly.

Zhu and his brother Zhu Dexin can whistle the song of a little sea bird, sibiguo, as the locals call it. "Only my family can imitate it," he says.

Carved from local bamboo, a whistle is about 8 centimeters long and 2 centimeters in diameter.

It's not too complicate to make, says Zhu.

Choose a small section of bamboo with a joint at one end. Carve out a tiny square hole 1 centimeter from the joint, the place where air flows out when the whistler blows it.

At the other end without the joint, cut a slanting "mouth" or notch and insert a small bamboo flake. That's where the whistler blows in.

Zhu's old whistle was soaked in salt water for several weeks, but after decades it still stays firm and sounds crisp.

Making a whistle is easy, but blowing it properly requires considerable skill.

A skillful whistler changes the air pressure and air speed and uses the tip of his tongue to imitate different tones and tunes.

"It's not a musical performance," he says. "You have to make sure which kind of birds are in the air and then communicate with them patiently and carefully," Zhu says.

Even when it's 300 meters overhead, Zhu knows the species and the call.

"The bird will think the whistle call comes from another bird telling it to alight on the ground," he says.

It is a seesaw battle of wit and patience between birds and whistler.

If you want to lure the bird down to the ground, you have to blow cheerfully at first. After receiving a "warm invitation," the bird will nosedive toward the sand after circling several times to confirm the signal in the sky.

But it stays alert and walks back and forth near the net. "Now I have to 'chat' with it," says Zhu. "The bird sings and I whistle back."

The conversation goes on for several minutes until the bird sets its mind at ease and steps into the net, which is flat on the ground.

From April to December, large flocks of migrant birds fly past the beach where Zhu now casts his net for purposes of science.

"Every year our father took our family to the seaside to catch birds," Zhu recalls. "It was such a long time ago and we were only teenagers, but I still remember clearly the magnificent view of thousands of birds hovering above the beach."

Catching birds used to be profitable because fresh fowl was delicious.

In the 1970s, 500 grams of birds was priced about 1.50 yuan. But later biologists bought each bird for 2 yuan each.

"The price was even higher when the bird's foot was tagged with a metal ring covered by foreign words I didn't understand," Zhu recalls.

Thus he learned from experts that many birds were from Australia and flew to Chongming Island to spend the winter each year.

In the late 1980s, catching birds was strictly forbidden by the government and bird whistling gradually became a kind of entertainment and folk amusement among villagers.

With the help of the local government, Zhu and other whistlers began to give performances as they toured towns and neighborhoods.

In recent years, Zhu and his fellow villagers have found their niche - using their whistle to help researchers investigating bird flu.

"We blow the whistle to call the birds down and experts check if they are infected with the flu virus," he says.

Zhu and his fellows have turned from bird hunters to bird lovers.

Not long ago, Pudong International Airport invited them to try to disperse birds above the airport. The avians are a nuisance and can pose threats of bird hits if they are sucked into aircraft engines.

"This was difficult for us," Zhu admits.

"The planes' engines are so loud the birds cannot hear my whistle."