My Cockatiel is acting strange

Question
My Cockatiel is down in the back corner of (his?) cage.  He is about 10 yrs old and he sits all fluffed up rocking.  He also has a real nasty attitude right now.  I am hoping he is maybe nesting but I don't know if I should be worried.  And no I am not sure it is a male.  If this sounds like normal behavior in a bird his age I would like to know if not I need to find a bird doctor.

Answer
Sam,

Are you sure your cockatiel is a male?  It could be a nesting male, but very often I see females behaving like this when they are getting ready to lay eggs.  Normally when a male is acting like this he is protecting a dark territory, not the bottom of a cage.  In any event, I don't think that he is ill.

Thanks for writing!

Cindy