I have two black-headed caiques, both about the same age (approx 6 years old). Ricochet I got as a weaned baby, and Elwood was my father's bird. I just got Elwood this year, as my father remarried, and in combining households with my stepmom, it was impossible to find room for Elwood's cage (small mobile home). Elwood was obtained from a parrot fosterer about 3 years ago. Both are DNA sexed males.
Elwood is your stereotypical happy go lucky caique. Ricochet has always been rather "serious" and not at all goofy. He takes everything seriously, from eating to playing. Elwood hops around generally being a goofball.
Anyway, earlier this year, I finally got them to share a cage (originally Elwood's) and they've been doing fine. They play together, sleep together, etc. However, in the last couple months Ricochet has been getting increasingly territorial about the cage, to where he even tries to attack when I'm changing food and water. And he will rarely come out on his own. He also acts like he is afraid of me, although I have not changed anything about myself or the way I interact with them. Elwood has not changed in personality at all.
Ricochet has gone through "hormonal" stages before, starting when he was about 3 years old, and usually this was in the early spring. But it was seasonal, and didn't last this long. During his hormonal times he was intent on taking a pound of flesh whereever he could land his beak. He even leapt onto my head once and began stabbing at my scalp with his beak. I removed him by the simple expedient of peeling my shirt off over my head and he came off with the shirt which also served to protect my hands while I put him quickly back into his cage. But as I said this was seasonal, and he does not hide his moods, so you can readily see when he is in "seek and destroy" mode and avoid handling him.
He also has been the only caique I've heard about who has had a problem with plucking. This was intermittent and was not physiological, as he had a couple of vet checks and bloodwork done and there was and is nothing wrong with him. Since Elwood came to live with me, he has not plucked and has regrown all his feathers.
The most recent time I've been able to handle him was earlier this week. I came home from work to find that somehow I must have not quite latched one of the feeder doors on the cage, and both birds were out and had probably been out most of the day. Ricochet was on the wire dog crate, and had been there long enough to poop on the dog 
and on the floor. Elwood was on their cage. Considering I have three cats, they were fortunate, although the cats I think know somehow that it wouldn't be worth tangling with either of them. Anyway, Ricochet was only too eager to step on my finger to get off the dog crate and I put him on their playgym where he promptly climbed to the very top and stayed there for about an hour. When he finally did come down, he again stepped on my finger, but as soon as I put him back into his cage, he immediately got all "macho" and began posturing. You couldn't have paid me to stick my hand back in there at that point. 
So it seems like a territory issue? Could it be that he thinks it's his "job" to protect his territory and Elwood from "invaders"? I could put him into his travel cage for a few days and see if that makes a difference, but I worry he'll start plucking again if I separate them. I can deal with him like he is - it just seems too bad that a handfed and once-tame bird should end up essentially "wild".
Thanks,
