3yr old Quaker suddenly biting

Question
Hi there,
I got a 3yr old quaker (who I named Mojo) from a lady who had other birds that were picking on it about a year ago. He's a sweetheart, he loves sitting on my shoulder playing with my earrings, every time I walk into the room, he says "Hi Mommy!", and when I leave he says "Byebye!". He snuggles with me, and has always been nothing but gentle and sweet. I've brought him to class with me on occasion, and he's very social, great with people and kids and has never really been any kind of a problem. The only time I've ever seen him get a little 'tude is when a friend of mine goes by his cage, which I understand is just a territorty thing. He's always been fine with me going by his cage, in fact I'm the only one he allows within five feet of it. However, suddenly a couple days ago he's changed. If I go near his cage, he charges out and bites me. I try to pet him, and he bites me. HARD. If I so much as go into my room and say hi to him he starts hissing. What could possibly be going on with him?! And how do I get him to stop? I'm afraid that if he keeps it up, I'm not going to be able to keep him anymore. I can't have a critter around me that's going to draw blood any time I try to interact with it. What happened to my Mojo?

Answer
Hello Chris and thank you for your post.
I am sorry that it took so long to answer you, but I was called out on an emergency.
Have you been spending enough time with Mojo?  Any kind of change in routine can trigger a response as you have described, as can ANY kind of changes in the room that he is in.  The simplest things can set this type of reaction.  Things like a picture not hanging the way HE thinks it should, moving a piece of furniture, changing his cage, any kind of changes (birds, especially Quakers do not like change).  If you have moved something in the room that Mojo is in, try moving it back to the way it was and see if his attitude changes back.

Good luck and God Bless.
Dianna