Everything I have read, says that the girls are naturally the dominate ones and only submisive during breeding season.
When injury resulting in bleeding and mid air fights occur, I would think about intervening.
How long have they been together?
How large is the cage?
Maybe you could rearrange the layout of the cage by adding new perches in different positions, move food dishes, provide more food dishes, add/change toys and in general make the whole cage appear different so Oliver doesn't have her territoy marked out to defend.
Has this behaviour from Oliver towards Kalle just started?
If all else fails you may need to think about seperating them and having the cages next to each other so they can still see each other without the physical contact.
I am sure others will have more sugestions and maybe even someone else has had a similar problem.
Good luck with it all.
Oliver
Kalle
