I'll tell you a little story here, trying to be brief as possible. Last year, when I decided I wanted a pet budgie indoors again, I went and bought a little blue male from Wyevales, and called him Alfie. Wyevales have their birds in an aviary, which is nice I always think. Anyhow got him home, and it was obvious he was used to being handled, was immediately tame enough to want to get on my finger, come out of the cage, play on the floor with me with toys. He already had the white iris rings, and the black had gone from the beak, and the bar-head had moulted out, so I guessed he was at least 12 weeks old.
Move on another 6 weeks now. I had been a bit suspicious to be honest, the only other budgie that I had before with attitude and this amount of tameness turned out to be a hen. As I so wanted a cock bird that would talk, and with the season turning from summer to autumn, I knew I had to make a decision if I was going to put him out in the aviary in time to acclimatise to the temperatures etc before the winter set in. So in the end, I decided to get another male (Chippy) and put Alfie out. When I went to buy Chip, I also bought his sister, a beautiful grey hen. I put this grey hen into the cage with Alfie for the night, and ALfie was beside himself with excitement, and attempted to mate the hen instantly! I then thought, oh no what have I done.
Anyhow the deed was done, and Alfie and the new hen were duly put into the aviary, and Chippy became my beautiful talking house pet that he is today.
When Alfie was about 8 months old, the cere began to pale, and I feared he was ill. Not so. I have got to the point at last. Alfie is a hen, a very healthy, dark browned cered hen. So in my opinion, he changed sex. Make of it what you will, but maybe it can just happen.