mating behavior

Don't tell me to go get a book, and I know who the flamers are here in these
groups

I have 2 budgie pairs in a cage 3ft by 3ft by 6 ft. There are 3 nest boxes
for the two hens, and I have seen minor disaggrements because each hen
wanted the same nestbox. Today, I find both hens clutching each other
tightly, laying on the floor of the cage fighting. No blood, only injuries
are a few missing feathers on the back of the neck. I picked them up and
neither wanted to let go. Got them apart, checked them each from beak to
tail feather. Now one hen has her favorite nestbox, and the other pair are
in their own cage sitting side by side. Other than separate breeding cages
.. . . .