I've researched this one a bit. The objective with potty training is ~not~ to reward your bird with food for going potty. It is these cases where the bird with hold it in at all costs until the owner is around to reward it. So, instead just identify (or praise) it verbally. This actually works.
Everytime Tamber would let go in his cage, I'd say, "Good poop." No reward....just identifying what he has done. After a short time, he'd poop and say, "Good poop," all by himself. So now I am able to say, "Good poop," and he will let go, if he has to. This gives me a little control over it. I also ~never~ scold him if he poops, no matter where he does it. I'm okay about cleaning it up.
Apparently, a bird will go potty approximately every 15 to 20 minutes. You can also time this with when you want your bird out of its cage. Watch for it. Then let your bird out for about 10 to 15 minutes. If you are training him, you can say, "Go potty" when he is in his cage and then let him out again after the deed is done.
Having said that, I will add that invariably, if Tamber gets spooked (which happens more out of his cage rather than in), the first thing he will do is fly somewhere and the second thing is poop. Birds will be birds.
Best wishes,
Deb
a.k.a windharper