The way i did it and sadly had to kill over 100+ adults due to over breeding.
I have 10 throughs full of yellow berrys, 5 full of stone, 5 of meat. Had 4 owls above on ledges. Had just 2 adult male and females gachas on wander in a building 500x300 foundations.
Came back 24hrs expecting to find them dead, and couldn't get in the door as there was so many of them. When i got in there, there was a lot of dead babies, whilst i was there though the adults we're killing some of the babies.
So looks like once they get to a point that no more will fit in there they kill there own young...
I checked the throughs and they were empty but only a handful of adults had low health. The rest were at full health.
My owls were and 3/4 health so don't think they fed much.