funny sunconure behavior questions?

[skeetersunconure]

what does it mean when birds bob thier heads? sometimes it is slow and relaxed like dancing sortof other times it is very rapid and sometimes ill be petting him or he'll just be on his perch and he does it its hard to describe so here is a video that i found on yt that shows it also what does it mean when they i dont know it sounds sortof like a birdy hiss? thanks!

[Pola]

i dont know but my conure does it too