6 Parrots per 5 Breeding Caves, How do you decide?

Hello,<br><br>Here is my issue. I currently have 18 breeding caves and 21 breeding pairs. 6 breeding pairs are waiting for available breeding caves. I have 2 breeding pairs of cockatiels, 2 breeding pairs of Indian ring necks, 2 breeding pairs of bourkes parakeets. The rest are either zebra finches or chestnut fronted macaws.<br><br>The problem starts with the parrots. Cockatiels, Bourkes, and ring necks have all had parents kill a chick in the past, so I am only putting 5 pairs per 5 breeding caves. In the future, I would like to get more breeding pairs, specifically 3 more pairs of Indian ring necks. <br><br>My question is how do you decide which pairs to place with 6 pairs per breeding cave, and which pairs to place that get more space, 5 pairs per 5 breeding caves? <br><br>Thank you in advance!