I've been raising gouldian finches for 5 years now, and haven't yet matched the success of my first season. That year my two pairs raised 22 babies. Almost every egg hatched, and 100% of the babies survived.
Last season went a little differently. I set up 5 breeding pairs in cages. Only 2 pairs laid eggs. Only about 75% of their eggs hatched, and when the parents (both sets) started tossing their newly hatched babies from the nest, I rescued the babies and the remaining unhatched eggs, put them into the nests of my society finches.
I have used society finches as foster parents in the past and they have never failed to accept babies or eggs as their own. But this time they, like the biological parents, tossed the babies from the nest.
The job of raising these little ones was left to me. I enjoy hand feeding baby birds, and have raised quite a few of them, but never tiny new hatchlings. This turned out to be a very time consuming task that I'm not anxious to repeat.
During that time, my sleep deprived brain gave a lot of thought as to what I was really looking for in this hobby and what would be best for my birds. And the answer that I came up with is no more cage breeding. I love watching the birds fly free in the aviary and if they could talk I'm sure they would tell me that they much prefer the freedom of the aviary over the confinement of breeding cages.
So, this year I hung nest boxes along 2 walls of the aviary and the birds are having a ball - laying eggs, raising their own babies, peeking into the other nests (they're very nosy), and chasing away others that get too nosy.