First, a little background of my bird. He is an 8 month old GCC, hand fed and well socialized.

I would like to begin with the backstory to what has occurred recently. My GCC Lenny recently made a trip with me to Las Vegas where I live, we stayed for a month, and we are now back home. As a gift for xmas I was given a new, bigger cage for Lenny to live in. He has been in the cage since monday morning now. I do have a vet appointment for Friday scheduled because I understand the last month has been very stressful.

Also, I got him a new sleeping tent that he will not sleep in so we are using his old cage as a sleeping cage. I was putting a perch back into his old cage, and as I was reaching into the cage he jumped at me and viciously attacked my hand. I put him down and was able to get the perch in the cage, but he went back for my hand again. He seemed to get set off by the clanging of the washers and the wing nut of the perch. When he came after me he puffed up and his tail feathers became sprawled out. He gets this way with food too, and some of his toys.

I understand he is becoming territorial and he probably very stressed. I just want an idea how to prevent him being so territorial. He is an extremely nice bird otherwise.

Your exactly right, he's being territorial and feels he has to defend his home. The new cage, tent etc., he just needs a week or more to get used to feeling "secure" all over again in this new home. New is not what he's used to and time is all that will heal. He's the same good bird, he just needs some time left in the new cage for a day or two, maybe three and he'll calm some. After the much needed acclimation time (however much time "he" feels it'll take"), he'll then be jumping for you finger for attention and instead of a bite. Just give him as much time as you can, we humans tend to be impatient and pushy when it comes to getting what we want, but we must consider most of all...what the bird needs. Not a thing you can do except nothing at all, give him time and understanding.