My boyfriend and I have had a lovebird for a couple years. She has always been sweet and loving to him, and tolerates me. I can hold her and everything, but I cannot get her out of her cage. The past few weeks have been different though. She has bitten my boyfriend several times for being inside her cage, she refuses to come out to him most of the time, whenever she is out of her cage she is very antsy and desires to be back inside it, she has bitten him when he touched her food dish, and has just been very territorial. She is not without food or water and nothing about our apartment has changed. She seems very withdrawn in a sense that she doesn't want to be with anybody. She's eating healthily and drinking normally. She takes baths and plays with her toys. She does not appear to be sick - what could be the reason for all of this?