Hi Glenna,
When you have a group cage, there are two rules that if not followed, will generally result in fighting. Always have an even number of birds in the cage, and never introduce nests or anything to encourage nesting. I’m sorry you lost your one little guy. Unfortunately, this disturbed the balance in the group. Each pair was bonded in their own way. The two that didn’t seem very bonded, just share a different bond than the other two shared. With same sex birds, sometimes the bond is as strong as a male/female bond, even to the point of mating and trying to nest. And other bonds are not as obvious, such as with your two that didn’t seem very bonded. You can now see they do have a bond, and now that it is being challenged, one bird is being more dominant and making that bond known. Sadly unless you can get another male that gets along with the now solo bird, you can’t return the single bird to the group cage. I would try getting another male – around the same age, or at least not a new baby – and place it in a third cage next to the bird who lost his companion. Give them time to bond and hopefully they will. If so, put them in the same cage to see how that goes. With budgies, they are very social so normally most males will get along. The females can be a bit more temperamental when it comes to a companion. If you can get a new bird to bond with the other, then eventually you should be able to have all four in the same cage. What you might do is switch things up and put the newly paired males in the big cage, and once they are used to it, return the other pair. This can generally work and while there might be some harmless sparring, they should work everything out.
Thank you for asking Lafeber,
Brenda
