No. Rhubarb leaves are loaded with oxalic acid, which can cause kidney failure in birds — avoid the whole plant.
Keeper's noteGarden risk: if your bird joins you outdoors, remember rhubarb patches are at perfect beak height.
Why rhubarb is dangerous for parrots
Rhubarb leaves contain high concentrations of oxalic acid and soluble oxalates, which bind calcium and damage the kidneys. The stalks contain less but still enough to matter for an animal a parrot's size, so the safe call is to skip the plant entirely.
My parrot already ate some — what now?
Remove all remaining food from the cage, note what and roughly how much was eaten, and call an avian vet or an animal poison control hotline immediately. Do not wait for symptoms — early treatment makes the difference.