Lucknow, Apr 5 (IANS): In a rare and a first-of-its-kind phenomenon, a Silver Pheasant, a bird belonging to the peacock family, has changed its sex from female to a male.

Confirming this and terming it a kind of "sex dimorphism", zoo director Renu Singh told IANS that the phenomenon had surprised most of the staff in the zoo.

The change was noticed by her some time back when she found the female in the bird enclosure shed not only her diminutive shape and size but also change her dull brown colour to a more vibrant colour of a male, which is often used by the polygamous male to win over female species.

The female has also stopped laying eggs and has undergone all "phenotypic changes" though from a distance there seem to be no changes anatomically, Renu Singh said.

She said that secondary sexual characters in the bird had definitely changed.

Zoo officials are now tinkering with the idea of seeking expert opinion on whether the lone ovary that this bird has is functioning normally or is it also in for some change.

The other sign of the sex conversion is the fact that her male partner is now seen fighting with her, now him, as no two male pheasants are known to co-exist in peace.

Zoo authorities have added another female to the cage for a "blissful life" however.

The 23-year-old bird has hence become a subject of mystery for the wide-eyed select group of officials but also for the researchers who would soon be conducting a study into the sex change.

Asad Rahmani of the Bombay Natural History Society has been informed of the development and zoo authorities are seeking guidance on the matter.