Today was an exception - I kept my hair up, that is until Piper made it quite clear that it was a bad thing. While he wanted to be on me, he was conflicted with the hair being up and kept flying right next to Zuri. Not going anywhere free of a bird, no, he targeted wherever Zuri was. Since this was a bad thing, I took the ponytail out and Piper flew back to my shoulder in a matter of seconds.
I have heard stories of people having issues with their birds when they've died their hair, had different coloured nails or even if wearing glasses when they normally didn't. I don't think I quite heard anything involving hair being up or down, although I'm sure Piper isn't the only one feeling the way he does about it.
In any case, I know not to have my hair up around him, lest I want him to put himself in a dangerous situation..