"Spontaneous sex reversal has been described as the result of pathological conditions (e.g., ovarian cyst or tumor, diseased adrenal glands) which cause the left ovary to regress. Residual tissue in the right ovary proliferates in the absence of a functional left ovary. This regenerated right gonad is known as an ovotestis and may contain tissue characterisitics of the ovary, the testes, or both. There are reports of these ovotestes producing semen capable of fathering offspring. "
"The "ovotestes" are steroidogenically functional and secret androgens, as well as estrogen. As a result, the bird develops male secondary characteristics. So while the bird is genotypcially female, it will be phenotypically male."
"If these changes to the ovary occur sufficiently early in the life of a bird, full development of functional sperms and the rest of the reproductive tract may result, and the bird can be fertile under these circumstances. This situation has been reported to happen in chickens. In 1923, one investigator reported natural sex reversal in several chickens in which testis-like structures and other normal components of the male system developed. One of these birds was reported to have sired offspring, a finding that indicated a major sex change very early in the life of this bird. It is notable that in all recorded cases of sex reversal in birds, the change has always occurred from the female to the male, not the reverse."
