aggressive cockatiel all of a sudden

Question
We've had our cockatiel now for about 8-9 years. He's been a good, well behaved bird up until this point but has started acting VERY aggressively. He will fly at your head as if to attack and will bite you, scream and hiss at you. He only does this in his room/cage. If I take him out to another room he doesn't do this. I'm very disconcerted because he's been such a dear pet to me and I don't know what to do with him when he attacks. We have never mistreated him.

Answer
Hi, Julia,

It's the very beginning of breeding season.  Could your male tiel be suffering from hormonal overload?  It's the time of year when sexual hormones start running rampant.  Also, birds tend to become very territorial over their cages/their space.  Often times when we invade this space, they react aggressively.  This could explain why he is aggressive when in/near his cage, but not elsewhere.  Is his cage large enough?  Poor diet can also explain this type of behavior.  What type of diet is your bird on?  Poor diet can affect a bird's behavior negatively.  Has anything changed in the bird's environment?  Sometimes changes can affect a bird's behavior.  There's not much you can do when the bird attacks except to tell your bird "bad bird" and put him back in his cage.  However, you can avoid situations where your bird will attack.  If he only attacks when he is out and in his room/cage, take him away from his room/cage when you let him out.  I can't offer more advice unless I have more details about what is going on.

Chrys