aggressive zebra finch male

Question
I recently had a zebra finch male kill another male. They are from the same parents but from different clutches. I put the aggressive male who was plucking everyone into his own cage which is next to the one with the other birds. Can he live alone or will he need company? I am afraid to put a bird in with him because of the brutal way he attacked the other bird.

Answer
There are two things you can try:
1. Put him in a separate cage where he can only hear the others but not see them. Keep him there for a couple of weeks and them place his cage beside theirs. Do this for a couple weeks and them put him back with the others.
You have to watch him very carefully in the last step to make sure he learned to be good. If he hasn't, the process needs to be repeated. It usually only takes a couple of time for this to work.
2. This one is only to be used when the first has been tried a few times with unsuccessful results.
What you do is remove him from the cage and put him in his own; but instead of leaving it where he can hear them you put him where he can't hear or see them. Again you do it for a couple weeks and then do what you did in the first one.
I don't like to do this technique unless absolutely necessary. Zebras are social birds and for one to be alone may cause depression. Should you see signs of depression (you'll know it when you see it), put him immediately with the others.

It is very important for both that you do not give him the attention the other birds normally would. What you're basically doing is giving him a time out. If you give him the attention, his personality won't change and may become worse.