#territorial aggression

Depends on whether it’s territory aggression or possessive aggression. 

Prior to implementing any methods we have to ensure there isn’t an underlying cause such as mistrust, hormones, fear or physical positioning which may be affecting the aggressive outburst.  If any of those things are present we must work to correct them, if they are not then we can assume it is solely a territory or possessive based aggressive response.

With territory aggression you want to accustom the bird to you working in those surroundings, typically the best method to negate the behaviour is teaching an incompatible behaviour like stationing, get the bird to station on a particular perch to earn a reward. Having the bird stand on a particular perch is incompatible with biting or chasing you out of a cage, they want the reward so they’ll let you muck around the cage until they get their treat, if trained correctly.  Over time the bird will remain calm the entire time you are working around the cage and the entire aggressive behaviour will fade.

Possessive aggression is essentially resource guarding, they display aggressive behaviour around food bowls or other essential resources. This aggression is a bit harder to work with because it has a very strong motivational drive, working in small increments and reinforcing wherever possible will aid you here.  Typically with these the best thing to do is to avoid circumstances which cause this behaviour (remove the bird from the area), divert their attention (give them something else to play with away from the cage), reinforce calm behaviours when you approach the dish in small increments or interrupt the aggression with an incompatible command.

To prevent these aggressions from occurring in the first place we can:

Change the cage layout frequently

Play games, target train in and around the cage

Move food bowls slowly, feed our birds out of food dishes on occasion

Change food bowl locations

Ensure they have plenty of resources; food, space, enrichment

Change the contents of the cage frequently

Give them more than enough territory; playsets away from the cage, different rooms, move playsets around