Follow-up:
Aggression is very costly for any organism, not only due to the energy it takes to engage in a display and attack, but also due to the risk of injury involved with "picking a fight". So for an animal to engage in aggression there are only a handful or reasons.
1) Play, which would not necessarily be inappropriate, and should not really be considered aggression per se, but is easily confused with it.
2) Fear aggression, which is the most likely and the most dangerous in any animal. This would primarily be seen when they don't have an escape such as when someone reaches into their cage or somehow grabs, corners, or restrains them. From the description of this situation it certainly doesn't sound like fear aggression.
3) Dominance displays to keep or obtain status. This may very well be what is going on here. If so other signs of dominance displays should be observable.
4) Resource defense / mate guarding. This can somewhat overlap with fear aggression as it may occur when someone reaches into the cage or handles a food dish. But this type of aggression can also be seen when there IS an escape route, but escape is just not an option. A parent guarding an offspring could be a good example. In pet birds this is probably seen mostly when someone new comes into the home. This form of aggression also does not seem to fit the description.
Lastly there are two other situations which would not likely be considered separate 'types' of aggression, but rather are unique subsets of these. One is if the bird is injured, if they are in pain they may "feel as though" they are under attack and they will fight back against whoever happens to be closest. This should not be overlooked as it is easy to wonder why they are aggressive while we completely overlook the nasty cut they have.
And finally a seasonal misfiring of proximate mechanisms... Spring time hormones. It's mating season for many birds, and if it is for yours their hormones will shoot up in order to drive them to find and fight for a mate. With no conspecifics to fight with or mate with we as owners can become the target of both of these behaviors. Currently I think Auggie is getting a bit randy, when he gets a little crazy he goes back in his cage where he can go .... um ... mate with himself.