A bird with a terrible voice and flesh too hard to cook
The flesh of the peacock is so hard that it does not rot, and can hardly be cooked in fire or digested by the liver. Its voice is terrible, causing fear in the listener when the bird unexpectedly begins to cry out. Its head is like a snake, its breast is sapphire colored, it has red feathers in its wings, and has a long green tail adorned with eyes. If it receives praise for its beauty, it raises its tail, leaving its rear parts bare. When it suddenly awakes it cries out, because it thinks its beauty has been lost. It is a bird with great foresight. Its feet are very ugly, so the peacock refuses to fly high in order to keep its feet hidden.
The hard flesh of the peacock represents the minds of teachers, who remain unaffected by the flames of lust. The fearful voice of the peacock is like the voice of the preacher who warns sinners of their end in hell. The "eyes" on the peacock's tail are to signify the ability of the teachers to foresee the danger we all face in the end. The raising of the peacock's tail when it is praised should remind us to not let pride from praise affect us, so we do not expose our ugly vanity.
The Aberdeen Bestiary, following a biblical quote saying that Solomon sent expeditions to bring back peacocks, has a two page sermon on the allegorical meaning of this theme.
Pliny the Elder [1st century CE] (Natural History, Book 10, 22-23): The peacock is conscious of its own beauty and takes pride in it. When praised, it spreads out its feathers to face the sun, so they shine more brilliantly, and curves its tail to throw shadows on its body, because the colors there shine more brightly in the dark. It is pleased when others look at the eyes on its tail feathers; it pulls them all together in a cluster for this purpose. When the peacock's tail feathers drop out during the fall moult, it is ashamed and hides itself until new feathers grow in. Peacocks live for 25 years, but their colors begin to fade at the age of three. Some say that this bird is spiteful as well as ostentatious. The orator Hotensius was the first person to kill a peacock for use as food; later Lurco made great profits in the fattening and sale of peacocks for the table.
Aelianus [170-230 CE] (On the Characteristics of Animals, Book 5, chapter 21): The Peacock knows that it is the most beautiful of birds; it knows too wherein its beauty resides; it prides itself on this and is haughty, and gathers confidence from the plumes which are its ornament and which inspire strangers with terror. - [Scholfield translation]
Martial (Epigrams, xiii, 70) "You are lost in admiration, whenever it spreads its jewelled wings; can you consign it, hard-hearted woman, to the unfeeling cook?"
Augustine [5th century CE] (City of God, Book 21, chapter 4): For who but God the Creator of all things has given to the flesh of the peacock its antiseptic property? This property, when I first heard of it, seemed to me incredible; but it happened at Carthage that a bird of this kind was cooked and served up to me, and, taking a suitable slice of flesh from its breast, I ordered it to be kept, and when it had been kept as many days as make any other flesh stinking, it was produced and set before me, and emitted no offensive smell. And after it had been laid by for thirty days and more, it was still in the same state; and a year after, the same still, except that it was a little more shrivelled, and drier.
Isidore of Seville [7th century CE] (Etymologies, Book 12, 7:48): The peacock (pavo) takes its name from the sound of its voice. Its flesh is so hard that it barely decays and is difficult to cook.