There are two of these wonderful little birds who are half-tame. They come, sit on my knee and take food from my fingers. They would prefer it if I would just open a bucket of worms. One of the little fellows likes to hop and climb over my chest, look in shirt pockets, pull at my chest hairs, perch on my shoulder and head. I think he is a nutcase. An entertaining nutcase.
It would seem that you are a replacement mom to that little fellow. When he perches on your head he may be looking for nesting material!