When did the sparrows settle in the Liu family yard？ Nobody can tell for sure. Maybe the day the family moved in， when Mrs. Liu moved a nest from inside the house to a tree in the yard. Maybe it was the day when she spanked her son and denied him dinner for shooting the birds with a sling. Or maybe it was the day when the Liu family planted the first seedling – the family planted hundreds of them every year. As the trees grew into a forest， the number of sparrows in it also increased exponentially.
　　How many sparrows are there in the Liu family forest？ Nobody knows. In spring， newborn sparrows stick their hairy heads out of the mountain-like haystack in the yard， chirping and hollering for food from their mothers， who came in such a large number that even the huge haystack becomes hidden from sight. In summer time， the willow that takes three adults to encircle with outstretched arms is densely covered by sparrows. If you stand under it for even a few minutes， your hair and clothes would certainly be stained by their droppings. In winter， sparrow nests stand out in plain sight in the barren trees – several of them in each tree， and there were more than 20，000 trees in the forest.
　　People passing the forest often frown and mutter to themselves， “What pests they are！” “What damage they might do to the crops！”
　　The Liu family， on the other hand， did not think this way. Despite the fact that sparrow chirping could be a bit noisy in the morning and evening， these birds made no trouble at all. The family didn’t see them as pests， and so left them alone in the forest.
　　As the community of sparrows grew， something uncanny happened in the summer of 1995.
　　The Liu family planted 6.7 hectares of cotton， which demanded tedious care year round from watering， weeding， topping， applying pesticide and so on ... Suddenly， disaster seemed about to strike and destroy the efforts of a whole year of labor when bollworms caused havoc across the field. It seemed all the cotton seedlings would be ruined before the pesticides could be applied. Mrs. Liu became so distressed that she had no appetite to eat during the day and could not sleep at night.
　　One evening， the helpless woman went to the largest willow in the forest. Looking up into the tree， she pleaded， “King Sparrow， you live on my land， and I have never bothered you. There are worms in my cotton fields now， can you please lead your flock of sparrows and eat them all.” 　　The next morning she went to the field to deliver pesticides. On the way， she saw a few sparrows on the power line. “Come for the worms， birdie.” The birds replied with chirps. Soon more sparrows landed on the lines. Surprised， the woman thought to herself， “Are they holding a meeting to catch the worms？”
　　As if a shot had been fired， the sparrows took off into the sky like a huge dark cloud， but soon dispersed into a dozen of smaller clouds darting toward the cotton field. After they dispersed into the crops， sparrows could be spotted on almost every cotton seedling， pecking at the worms. From time to time， they would raise their heads， and look around with composure. When people approached， they would hop to another seedling unafraid， and continue to hunt for worms.
　　For the next two weeks， sparrows left their home in the forest every morning， and gathered on the nearby power lines. Once a silent command was given， they would swoop down and head off toward the cotton field like a regiment of well-organized squadrons. They covered the land one patch after another， and within two weeks all bollworms in the 6.7 hectares field had disappeared.
　　Putting aside the heavy pesticide sprinklers， the Liu family stood by the field， watching in amazement the sparrows’ battle against the worms. The longer they observed， the more amazed they became. What was happening in front of them should have been possible only in fairy tales.