cockateils behavior

Question
Hello,
Can you tell me please what it means when a male cockateils gets all upset when another bird comes to his certain area?  I have 5 cages on the ground with plenty of room for the 15 birds to fly and move around, but whenever another bird comes to the corner where he normally hangs out and sleeps at night, he gets aggressive and opens his wings and hisses at them.  Even me, if I try to reach out to him.  He just started doing this about a week ago, and I dont know why. He only allows 2 birds into that area.  They sit on top of the cage like a king and queen, and he wont allow another bird in the whole area.  Just these 2 other birds. (a male and a female)  Thanks for any answer you might give me....I will wait for a reply.  Josie

Answer
It sounds like your territorial male could be a hen. What makes me think that is the spread wings and hissing, a totally female trait. Especially if it is spreading it's wings and hissing while swaying back and forth. Are you sure of it's sex?

If it is a male, it is rather unusual behavior. You may want to consider getting him a mate and caging them together alone for a while, so they can bond. You could separate him alone, just long enough so he loses claim to his territory, but I tend to think tiels are happier with mates.

Let me know if you are sure of it's sex, and if separating him for a while works!
Thanks, Julie~