Random things that scare your bird

Yeah, that could be it! For awhile, my bird would look at me suspiciously if he saw me without my glasses. We have a silly little greeting we always do, and he would very tentatively do his part of the greeting if I went into his room bare faced. I'd respond, and he seemed to eventually figure out that it was still me with or without the glasses. However, now I'm wondering if many he just thinks "no glasses" me is another person that he just eventually learned to trust.