I have had Snoopy since a baby and she has always loved riding on my shoulder. I had started to do this before I found out that there could be a question about it's advisability, and it would break both our hearts to stop now. If she wants a head scritch she will touch my ear with her beak or sometimes stick her beak into my ear. If I am doing something with food and she wants a taste she will lean around and plant "butterfly kisses" around my mouth. But here is the interesting thing. I always wear a hand towel draped over my shoulders when carrying her. This is partly to catch the poop, but also to give her something to hold onto, since being in the tropics I pretty much live in tank tops and bathing suits. On the rare occasions when something upsets her and she wants to bite, she will bite the towel, which is my signal to get her back to her cage.
I don't think I would ever have the courage to let a big bird like a Macaw on my shoulder, though
Oh, BTW, I did manage to teach Snoopy to leave my earrings alone!