its easy (i potty trained rusty to do big poops in the morning on a handy towel that i hold out for him - then he poops, gets a kiss and he is happy as - then does lille poops throughout the day but doesn't like pooping on ppl).
you just say poop every single time he poops, mornings is when they like pooping - so pick him up - say poop and wait, then he poops, say poop again, give him a treat - he will like that and associate the word poop with pooping.
voila. potty trained bird.
rusty hops on my finger, tenses up in the morning and does a great big poop on the handy towel that i chuck away.
birds are actually clean animals, so will only dirty their surroundings if they have to.... give him an alternative - my crows had a lille sand box that they pooped in.