It's a delicacy sold for a few dozen yuan amid hushed tones in certain markets and restaurants in Guangdong province. Sellers turn away customers who do not speak the local dialect - anyone caught can be fined as much as 100,000 yuan (HK$126,400).
Despite the threat of penalties, the market for yellow-breasted bunting, a migratory bird that flies from Europe to China for the winter, thrives on the mainland. Conservationists say poaching to supply the demand is a leading cause of the sharp decline in the protected species' numbers over the past decade.
The bird was today listed as endangered by the main global body that categorises the survival status of the planet's species, the International Union for Conservation of Nature. The union has two higher categories - critical and extinct in the wild - before a species is deemed extinct.
Guangdong made the bird a key protected species in 2001 - at a time when the union had it listed in its lowest category of "least concern".
But its numbers appear to have fallen rapidly. Experts are unsure exactly how many are left, but BirdLife International, a conservation group headquartered in Britain, has cited one study published in 2009 that estimates there were no more than about 10,000 migrating in China every season.
Another study published last year estimated the species' numbers had dropped by at least 70 per cent in European Russia in the decade to 2010.
Often known as "rice birds", the yellow-breasted bunting is a popular delicacy in southern China, especially Guangdong, where locals believe eating the animal can boost their sexual vitality and detoxify their bodies.
"The very rapid recent population decline in the yellow-breasted bunting is believed to be primarily driven by trapping at migration and, in particular, wintering sites in southern China and Southeast Asia," said Andy Symes, global species officer with BirdLife.
The birds usually flocked and roosted in large numbers in reed beds, making them vulnerable to poachers' nets, he said.
"They are mostly taken for food … [The practice] was formerly thought to be restricted to a small area of southern China, but has now become more widespread and popular owing to increasing affluence" among mainlanders, Symes said.
The deterioration or loss of their winter habitats due to changing agricultural practices could also be driving down numbers, Symes said.
The Guangzhou Daily reported last week yellow-breasted bunting was still sold discreetly at certain restaurants and markets in Dongguan, at an average price of 30 to 45 yuan.
"The birds are available when local people ask for them," said Tian Yangyang, a campaigner with Beijing-based environmental group Nature University.
"Information about such shops is spread by word of mouth among locals. But the dealers get suspicious and turn down outsiders who do not speak the local dialect. It then only becomes more difficult to uncover the illegal behaviour."