If you haven't heard of him, he is a very rare budgie. You could say he is two-faced.

That is really interesting! Do you think they will try to breed him? I wonder what offsprings he'll produce.

Very interesting....
I've not seen a budgie looking like that...
1st off I thought someone had been messing in
photo shop!

He can't. A Halfsider is sterile. That's why they are so rare.

Amazing!
How do they know that halfsiders are all sterile?

How do they know that halfsiders are all sterile?


I was wondering the same thing! Maybe they tried breeding them but their eggs were never fertile?

Well, if that's how they know it, it's not 100% certain and there is always the possibility that one of them is gonna be able to reproduce.
Thing is, it might be a genetic trait that won't pass along to their children. I am very curious to know more about this.
The commentator said it's a rare phenomenon that happens to humans as well, merging twins (sounds like something from a horror movie lol), if so I doubt it would transmit to the children.

"A Halfsider is when 2 sperm fertilizes 1 egg with 2 yokes (that's why they are so rare!) So in turn you basically get 2 budgies in on full body, kind of like a twin."

Found on TB. Not much else on it though. Nobody really has one, so no good information on them. His owner just said Twinzy was sterile.

They're not always sterile! This is a chimera, caused by two different zygotes fusing into one individual. If it's a male/female combo it will probably be sterile. But if both sides are the same sex they can sometimes produce normal offspring who aren't halfsiders, and the color of each offspring will depend on which "side" the ovum or sperm came from.

My massive article on the Schimmel cockatiel talks about this: http://www.littlefeatheredbuddies.com/i ... immel.html If you scroll down past the cockatiel pictures and the observations on those pictures, you'll come to a section that talks about mixed DNA. It'll tell you about several different kinds of genetic oddities, including chimeras.

Since a chimera starts out as two different individuals, it's probably true that there would have to be two different egg yolks that got enclosed in the same shell.