Reveal the principle of parrot fortune telling

Don't trust the best of these fortune tellers! You stand in front of him, tell him your name, and see if he can figure out your birthday ... These fortune tellers are all veterans. With some book knowledge and faster hand movements, you can fool ordinary people, similar to magicians using magic, but not as easy to crack as magicians ... First, you choose a piece of paper with a surname on it, and you think only you can see it. He already knows your last name, so put what the parrot usually eats or the smell that the parrot is familiar with on the same last name paper, and the parrot will of course choose that! These parrots are trained at home. How can something so amazing happen in .........................................................................................................................................................................? Why science? They all go to tell fortune ... but some old people do have special abilities, but these are a few after all, and they will not come out to help others make money unless they need help!