Someone posted on here that they had a way that was told to them but was not proven by a doctor to work but it worked for her and her 3 Budgies and it ended up working for me. She said to look at they way they perch. If the Budgie's feet are spread wide open and stay wide with space apart, it is a Female. If the feet are closer together and more on the parallel side, like ski's when you are skiing... then it is a male. I tried that and I said, yep, BooBoo is a girl and then when we saw the bird doc again she confirmed it. Like I said no Doc. has said it is a proven fact. But maybe it will work for you and maybe you'll have some fun with it also!! Good luck and let us know!!!!
