I had 3 budgies to start with 2 males and one female. I recently rescued 4 from my college that were going to be put down if no one adopted them. I brought home two males and two females. My original male name Chester keeps picking on a new male that's only about 6 weeks old. Chester has already sent the new male named toby to the vet because he couldn't walk. And Chester seems to have bonded with one of the females we have so I'm not sure if he's jealous or territorial or whats going on but I'd like to prevent having another huge vet bill.

You have an uneven number of birds. There is a spare male, and until you get him a hen of his own, or possibly even another male to bond with, the odd man out will always be trying to cut in on another pair.

 

They don't bond permanently, so bringing in new birds means a shifting around of pair bonds, with them all vying for their position in the new flock, and competing for the best mates. It would sort itself out more amicably if there was an even number of birds.

 

At the first sign of fighting, one of the fighters should be separated out until the cause of the fighting can be resolved. Waiting to "see what happens" will lead to bloodshed, vet bills, and possibly even death.

 

I would say to take out either the aggressor, or else if that one seems to be bonded with a female, take out the "loser", so the aggressor no longer feels he has to defend his position. Good luck! Let us know how it works out.