A rescue parrot who bites is usually not an aggressive bird. He is a bird whose earlier signals, a turned head, a step away, a raised foot, a quiet growl, were ignored until biting became the only language that made people back off. Rebuilding trust means proving, hundreds of small times, that you hear the whisper so he never needs the shout, and that your hands are no longer tools for forcing him anywhere.
Map his warning chain before you train anything
Spend the first stretch simply observing from a comfortable distance and noting what happens in the seconds before a lunge. For many parrots the chain runs from stillness and hard staring, to feathers held tight or suddenly fluffed, tail fanning, beak opening, and weight shifting forward. Your job is to respond at the first link, not the last: if he leans away when you approach the cage, you stop there and leave a treat in his cup. Each time a small signal successfully ends the pressure, biting becomes less necessary, and you will often see the softer signals return as he realizes they work again.
Train entirely hands-off until he chooses otherwise
Target training through closed bars is the safest bridge for a biting rescue. Present a stick target, reward any look or step toward it with a high-value nut delivered into a cup or on a spoon, and keep your fingers out of range. Short sessions that end while he is still engaged teach him that training predicts good things and then stops before it becomes too much. Do cage cleaning and food changes slowly, narrating as you go, and where possible let him move to a far perch or a separate area voluntarily rather than toweling or chasing him, both of which can erase weeks of careful progress in one afternoon.
Rebuild the hand's reputation separately
Do not combine early trust work with step-up requests. Let hands become boring and generous first: hands bring fresh food, scatter foraging pieces, rest flat and still below perch level, and then leave. If he bites despite your care, stay as calm as you can, avoid yanking away or scolding, set him down safely if he is on you, and calmly end the session. Punishment and dramatic reactions both teach a rescue bird that humans are unpredictable. Note the context of every bite, time of day, who approached, what was asked, because biting that clusters around cage defense, a favorite person arriving, or evening tiredness each calls for a different adjustment.
Protect the progress his history explains
Gather everything that came with him, prior diet, known fears, favorite foods, old vet notes, and the rescue's observations, and keep your own log of warnings, wins, and triggers beside it. That record matters because a new sitter, vet, or family member who does not know that he panics at towels or guards his food bowl can undo his confidence without meaning to. Share the warning chain and the hands-off rules with anyone who will be near him, and celebrate the quiet milestones: eating while you sit close, targeting eagerly, choosing to stay near the front of the cage. KinsLe's Pet Passport in KinsLe holds your rescue parrot's records together in one portable packet, ready for vet visits and handoffs, so the people helping him always know the history behind his behavior.