http://www.telegraph.co.uk/news/main...19/ixhome.html

Freaky the hen spent the first eight months of her life laying eggs and attracting the attentions of a rooster

But last September the silver-laced Wyandotte started crowing at sunrise and being aggressive.
She has since developed the full comb and wattle of a cockerel. She has put on weight and engages in simulated mating. Only the equipment to produce offspring is missing.
Her owner, Jo Richards, 42, of Saltford, near Bath, said: "One morning, out of the blue, she just started crowing. I have kept chickens for years but never heard of such a thing."
Victoria Roberts, the Poultry Club of Great Britain's honorary vet, said Freaky's condition was "very, very rare - about a one in 10,000 event." She said: "I have been keeping poultry for 35 years and seen it only twice.
"Only one ovary normally functions in a chicken, the left one. If that is damaged, by a tumour, for example, the other one kicks into life. The right ovary can begin to develop as a testis, producing testosterone which influences the male characteristics.
"These include the colour and shape of the plumage and a wattle and comb. Sometimes they even crow, but they can't fertilise eggs."
She added: "Sex change chickens are rare but they have been around for centuries." An old proverb says that "a whistling woman and a crowing hen are neither fit for God nor man."