During the early Eastern Han Dynasty, General Ma Yuan, while a minor official, once freed a group of prisoners he was escorting out of compassion and fled to Gansu to farm and herd. Later, his military achievements earned him the title "General of the Waves" and the rank of Marquis of Xinxi.
During his southern campaign in Jiaozhi, General Ma Yuan learned that his two nephews, Ma Yan and Ma Dun, were behaving frivolously—gossiping, mocking others, and befriending wandering knights. So he wrote them a letter of stern advice: "I want you to hear of others' faults as you would hear your parents' names—your ears may catch them, but your mouth must never speak them. A man who gossips is a man without virtue."
In a letter, Ma Yuan wrote: "Long Bogao (then Magistrate of Shandu) is loyal, cautious, and articulate—humble, frugal, and upright, earning great trust. I admire him deeply and hope you will follow his example. Du Jiliang (then Imperial Cavalry Commander) is chivalrous and righteous, sharing others' joys and sorrows, befriending both good and bad alike. When he buried his father, a crowd of friends came. I also admire him, but I do not want you to copy him. If you fail to match Long Bogao, you will still be a decent, prudent person—'carving a swan poorly still resembles a duck.' But if you fail to imitate Du Jiliang, you may become frivolous and reckless—'painting a tiger badly ends up looking like a dog.'"
Later, the idiom "Carving a Swan but Getting a Duck" came to be used to describe imitation that, though not entirely successful, still bears some resemblance, serving as a warning against aiming too high.
Source: *Book of the Later Han*, "Biography of Ma Yuan"
Meaning of the Idiom: Later, the Chinese idiom "刻鹄类鹜" came to describe imitation that, though not entirely successful, still bears some resemblance, serving as a warning against aiming too high.