shivering

So pikachu is shivering but When she is about to poop she gets all fluffy and shivery and bobs her tail once but after her pooping shes still shivering anyone know why?

I have a young Cockatiel (doesn't yet have the adult coloration young). I have only had him for a little over two weeks so he is still really scared. Ever since I got him he has done this thing where he puts his crest up then fluffs up and shivers like he is cold only when I or a family member...