My lovebird Zip is 13 years old and he's never done this before.
He was wandering about (under my watchful eyes) after a shower under the faucet and decided to begin exploring the corner of the wall with his beak. The wall, mind you, which I had just painted yesterday evening.
"NO!" I exclaimed. "Thou shalt NOT beak walls! That is NOT allowed!"
He just looked back at me, of course. I could speak Klingon as far as vocabulary counts, but the tone does help. It was clear that I was not pleased. He stopped for all of five seconds.
Normally I would herd him back to his cage at this point, but that option was not available since I was in the middle of cleaning said cage. Next strategy: Place some large and vaguely scary objects between Zip and the tasty-looking wall corner, like Kleenex boxes and liquid soap bottles.
My dear Zip is a bird of little brain. If I'm lucky, he'll have forgotten about this episode by the next time he exits his cage.