A hawk catches a sparrow, but when the hawk is about to kill it, the sparrow wisely suggests there may be a better killing place for the hawk. When they come to that spot, the sparrow immediately crawls into a dry yak horn and tells the hawk that if it claps the horn with its wings, the horn will break. So, the hawk uses all his strength to beat the horn, but in the process his wings become broken, and the sparrow successfully escapes.