I’m in the process of cleaning out the cages so I have returned all of the Zebra Finches to the main aviary. I also replaced the two (dead) potted grasses with alive (for now). A bit of greenery really makes the aviary looks nice and the birds seem to like it as well.
The two charcoal males returned to the aviary without issue (although the smaller of the two seemed to have poor flying stamina initially). I returned the pair of fawn Zebra Finches (nothing eventuated from the seven eggs they laid) and it turns out the male is quite the bully. He insisted on occupying a large perch and would let no other bird near it. The male grey Zebra Finch in the aviary is a solid little bird and even he was being pushed around. I was hearing squawks I never thought finches could produce. This was not good.
So late today I removed the pair of fawn Zebra Finches and placed them in a small cage indoors. The atmosphere in the aviary changed instantly. When I have cleaned out their cage they can go back in there.