A couple of hundred people, mostly men in leather coats with cigarettes in their mouths, were as usual milling around in the open air bird market at Guanyuan Bridge, when a bright yellow canary escaped and flew up high into a poplar tree. Immediately all trading stopped and everyone congregated to watch the fun.
The distraught owner, a middle-aged worker in a cap with big ear flaps, cursed his luck. The song bird sitting 40 feet up among the fragile branches, apparently stun ned into immobility by its sudden freedom, was worth about 400 yuan (£36), or two weeks' salary.
Within seconds a birdcatcher appeared with an extending pole like a long fishing rod, which he played out expertly until it reached the canary. The thin end of the pole was coated with strong glue and the little bird suddenly found itself stuck fast. The rescuer retracted his implement and plucked the canary off, leaving a few yellow feathers on the tip.
The owner was not particularly grateful, however, because under the unwritten rules of the Beijing bird market, once a song bird flies off the finder gets to keep it, and catchers with poles hang around waiting for such an opportunity.
"I'll pay you 200 yuan if you give it back to me," he pleaded with the poleman.
"No way! No way!" the catcher replied, turning to the crowd and shouting: "Who will give me 250?"
A few banknotes quickly exchanged hands and everyone went back to the serious business of buying and selling birds.
Losing a bird this way is not the only hazard for the sellers, who stand around all day in the cold displaying their beautiful little birds in transparent plastic boxes. Sometimes a thief will pretend to inspect a nice-looking specimen, then slip off while his friends distract the owner.
Song birds have suddenly become big business in Beijing. There is a tradition in China, where other types of pets are almost unknown, of raising song birds for display, and every morning old men take their birds to city parks in elaborate cages. But most of the people at the bird market these days are speculators.
Until recently the big money in street markets in Beijing was for foreign stamps, but about six months ago speculators withdrew from the stamp market, which collapsed like a south-east Asian currency, and invested instead in birds.
It was a scam on a massive scale. Black market manipulators spent one million yuan (£91,000) to buy up parrots in particular and hire people to buy and sell them at inflated figures, an insider told the Beijing Youth Daily. They made a killing and now there are thousands of get-rich-quick parrot breeders among the apartment blocks and back lanes of Beijing, all cashing in on the polly-bubble.
A pair of birds today costs about 10 times more than last summer. A couple of common brown-faced parrots fetch 200 yuan (£18) and two green-faced parrots, 1,200 yuan. A pair of particularly exotic parrots goes for about 18,000 yuan or the price of three television sets.
"I invested 10,000 yuan and got all my money back in six months and am now making more than I would at work," said Mr Gao, a former employee at the Capital Steel and Iron Works, where many workers have been laid off and are breeding parrots instead.
"It's better than investing on the stock market," said a man with several pairs of brown-faced parrots, as he offered me a cigarette, the essential first step in engaging a potential customer.
"There's no risk and even if the prices comes down within a few weeks you can get many more generations of birds."
A young man in an old army coat swinging a transparent box with two green-faced parrots disagreed.
"There is a risk," he said. "The parrots could die from a disease or the price could come down before you know it."
The secret of success is getting a pair of fertile parrots which will lay eggs quickly, said a vendor who was doing a brisk business selling "Professor Lin's Fast Breeding Medicine," guaranteed to make parrots go into heat and produce more eggs in a shorter time.
The Beijing bird market is not for novices. Sometimes sellers use hair dye to colour the plumage of a bird and get a higher price, and unwary buyers occasionally acquire two male parrots, which are apparently more plentiful than females, thinking they have bought a pair which will produce eggs.
One customer made just such a purchase and the word quickly spread around the market. But the seller, an old man with weather-beaten face and twinkling eyes, was unrepentant.
"Maybe he's not such a fool," he said. "Maybe he's got a pair of females at home."