I've been asked to contribute my take on amazon body language. So here it is. This is by no means an exhaustive list. If anyone thinks of things I've left out, and I'm sure there is, feel free to add to this.
Amazons more than any other parrot use body language to communicate. You can usually tell just by looking at them what they are going to do before they do it. People call them “moody” but it’s more like they are 100% honest about their feelings, and they can be rather “opinionated” at times. Sometimes that means, “Sorry, I’m just not interested right now.” When they tell you something like that, especially if they continue to tell you that, and you ignore it, then don't be surprised if they bite.
Wing flapping: (Usually accompanied by squawking.) If your bird is standing upright, and flapping at you, it generally means: “HEY DUMMY, I’M TRYING TO GET YOUR ATTENTION HERE, AND I’M GETTING FRUSTRATED BECAUSE YOU DIDN’T NOTICE.”
Recoil in Horror: (Usually accompanied by growling) This one is unmistakable. Fear, bordering on panic. It means (a) get that thing away from me; or if there is no object involved, (b) get that person away from me. (Often just before, “I’m either going to fly away OR I’m going to bite the crap outta someone. I just haven’t decided which yet.”) Show them something new, and this is usually their first reaction. Give it five minutes, it'll probably change to "That's mine" once they get used to the offending person or object.
Displacement/lunge biting: Here’s a clue! See this thing?! That’s gonna be your [INSERT BODY PART HERE] if you continue to do what, it looks like you’re planning to do. Just back away from the cage, and no one gets hurt. AMAZONS DON’T BLUFF. (That would be macaws.) This is not a test. It is a simple statement of fact. I am telling you right now, I WILL BITE YOU. DON’T YOU DARE LOOK SURPRISED WHEN IT HAPPENS… You were warned!
Big Bird: This is the closest amazons come to "bluffing." Wings spread. Making themselves look bigger. Standing straight up. "I'm the big bad birdie... DO NOT mess with me." They're not actually fixing to attack you. They just want to look menacing. And they are only bluffing to a point. If he's doing that, I wouldn't be in a hurry to stick your fingers within striking range. Normally they just turn in slow circles with their wings open. As long as you're not aggressive, they won't be either.
Head down and/or head feathers raised Scratch my head.
Wing flipping. I’m kinda tired and I find that annoying. I’m ignoring you now.
Wing flipping accompanied by eye pinning Apparently you don’t take a hint. We passed annoying a few minutes ago. I’m starting to get angry now. WHAT PART OF LEAVE ME ALONE DID YOU NOT UNDERSTAND?!
Poofed up, one leg up I am calm, content and relaxed. (And I’d like to stay that way, thank you.)
Standing straight up, foot up Pick me up!
Leaning forward, wings quivering I am in launch mode. Pick me up NOW, or I’ll come to you.
Strutting around in a STRAIGHT UP stance, eyes pinning, tail flaired, while whistling/chattering, and making silly noises at you: THIS is the amazon happy to see you dance. Interaction is required. I need it now. DO NOT IGNORE ME OR I’LL BECOME VERY, VERY UNHAPPY…
[WARNING: YOUR BIRD IS NOW APPROACHING AMAZON OVERLOAD. EVEN THOUGH THE BIRD IS HAPPY TO SEE YOU AND IS CRAVING INTERACTION, HE IS ALSO “IN THE ZONE.” HE WANTS TO PLAY. AND HOW DO AMAZONS PLAY WITH THEIR TOYS?! THAT’S RIGHT, THEY ATTACK THEM. BITING IS NOT A "MOOD SWING" AT THAT POINT. IT'S AN OVERSTIMULATED PLAY THING. Your bird does not suddenly hate you. Give him a second to calm down before picking him up. He'll be fine. Pick him up in the middle of the display? He might bite, even though he's happy to see you. Not because he's moody, but because he is THAT wound up...]
Strutting around in a HUNCHED OVER stance, shoulders hunched, head down, beak open, eyes pinning, tail flaired, WINGS HELD SLIGHTLY UP AND POSSIBLY QUIVERING, while chattering TERRITORIAL INTRUSION noises at you: THIS is the AMAZON LINE OF DEATH DANCE. Often mistaken for the amazon “happy to see you” dance, it means the exact opposite. And the main difference between the two is posture: Hunched over, head down, wings up.
You are intruding on my territory, and I will defend it to the death. Take one step closer and I will rip your lips off….
Defcon 1: Strutting and displaying.
Defcon 2: Lunge mode while strutting and displaying.
Defcon 3: Wings quivering. IF THIS ONE HAS PROGRESSED TO THE WING QUIVERING STAGE THAT BIRD IS IN LAUNCH MODE, AND HE’S AIMING AT YOUR FACE… [Take IMMEDIATE steps to protect it.]
There is no Defcon 4, and there will be no further warning before launch sequence is initiated. The order to remove your lips has already been given! Seriously, defuse this one before you get to the wing quivering stage...
There are also individual facial expressions:
The quizzical look — What’s that? I’m interested. (That doesn’t necessarily mean I want it anywhere near me, until I figure out what the heck that is…)
The “is that for me” look. (Which means, Both GIMME IT! And WATCH YOUR FINGERS WHEN YOU DO!)
My bird has a “come hither” look. That means pick me up, and scratch my head.
My bird also has a “go away” look which needs no explanation.
My bird has a “I’m getting jealous” look. Which essentially means, you’re with me at the moment, don’t make me pinch you.
My bird has a “I’m coming with you look. No really, I am, you’re not leaving here without me. Dammit You get back here and pick me up!” (That last part is no longer a look. It’s a look combined with a rather distinctive flock call.)
The birdie smile, also needs no explanation.
To me it looks like the head skritch feels so good she can barely stand it...sort of a birdy "skritch orgasm." Yeah, it sounds weird to me, too. So, it could be a begging behavior. 
