Bratty behaviour?

The Prof has started chasing Debbies feet and biting her heels when she turns away from him. When she goes to pick him up, he bites her, hard. 1st time, every time. The heel thing has been coming on slowly,for a while, but now he is marking her and making her scared to touch him. He still wants strangers to pick him up, but not Debbie. Any ideas where this bratty behaviour coming from?
He wont do it when I am watching, I have to hide to see it happen, or see the marks on her fingers.
He is defiantly disliking her as much she hates him. Its a mutual dislike thing. They are not buddies, but he is not allowed to monster anyone any time
How do I pull him back into line straight away?

The first thing that came to my mind is differential reinforcement: teach him to do something incompatible with biting on certain cues such as seeing her feet. Birds are great at learning routines, too good in fact, sometimes they get ahead of us and get upset when we don't follow through with the routine.

One example of an incompatible behavior would be going to a particular perch or place for a reward every time he sees her feet. The type of work you have done with him perviously will dictate the precise process but basically you show him the cue that puts him in attack mode - so first you observe, is it her feet, or just hearing her voice etc. You give that cue and get him to go to the perch and shower him with praise and a special treat (I've found some dried blueberries that work great for a training reward for auggie, but each bird is different.)

All this would in fact go smoother if you taught him a command to go to that perch first without Debbie around. Get the command solid and reward him every time he obeys it. Then see if she can give him the command, practice that. Finally have her give him that command every time he's about to attack (but before he does) still rewarding him every time.

Hopefully he'll catch on the the pattern and the command will become unnecessary - He'll see her feet, or whatever cue sets him off and he'll have a choice: attack and get whatever inherent reinforcer there is in that, or go to his perch and give showered with attention and a great treat.

Differential reinforcement, as awkward as it may sound, is the fastest and generally easiest way to get rid of unwanted behavior, especially aggressive behavior. I have been surprised by how well it works with birds, but again that is because they are gret at learning routines.

I hardly ever give Auggie commands anymore, he knows when I grab my keys for example that he needs to go to his cage for a reward. And he does every morning.

If you try this method patience is obviously important, but timing and consistency are more so.

Good luck.

Here is an example of one he did earlier,...
[ame="http://www.youtube.com/watch?v=Op8ZG0yeZ4M"]http://www.youtube.com/watch?v=Op8ZG0yeZ4M[/ame]
the same on photo http://s193.photobucket.com/albums/z110/RedBalloonubik/?action=view&current=footattack.flvbucket