Colony Breeding vs Closed Breeding
There are 2 different methods of breeding to consider if you are planning on breeding your budgies. The first is colony breeding where nestboxes are set up in an aviary with more than one pair. The second is closed breeding where one pair is placed into a breeding cage or cabinet with an attached nestbox.
I have often heard from people who "tried" colony breeding and met with disaster. Often it can be the case. If you are trying to breed too many birds in too small a space with nesting boxes ( and maybe not enough of them ) lined up on a shelf right next to each other....it IS a recipe for disaster.
To colony breed successfully you need to be available to watch over the dynamics of the aviary and the relationships of the birds at the time.
If You Intend To Colony Breed....You must check all these points:
There needs to be two feet minimum between nesting boxes for this to work.
You DO need twice as many nesting boxes as pairs of birds...so the hen can choose their nestbox.
Placing the nesting boxes with entry ways from different directions helps too.....i.e. Not all facing forward. Some sideways entry, not directly facing another birds entry. Kind of arrange them this way and that. You may need to screw some into the walls and not just rely on a shelf.
Try to have all nesting boxes at the same height as higher ones are mostly highly sought after by all birds.
Some times you need a piece of plywood placed strategically here and there so a pair's view from the entry of their nesting box is obscured from a pair of birds nearby. You can screw these dividing screen sections to the boxes concerned.
You also need to be sure that the pairs you have ready to cohabit and breed in that space are easygoing birds, none of the hormonally aggressive types that may get nasty with others.
Be prepared to watch the hierarchy in the aviary closely for a while off and on over some days till they all get settled within their own nesting sites and happy with their own partners. I
t's best if you can remove some of the birds for awhile and add each pair to the aviary again giving them time to select and settle in the chosen nesting box before adding the next pair.
Have more feeding cups/ stations than you normally do and try not to have a feeding area or main perch right next to a nesting box.
If you can put a slightly longer perch on the front of each nesting box that accommodates both male and female....it helps. It generally stops the male feeling he has to defend the top of his chosen nesting box from anyone who wants to sit for awhile or peer in.
If a pair of birds sits on top of a another pairs chosen nestbox and interferes with the "owners" coming and goings, put something on top of the nesting box to stop that happening...maybe an upturned plantpot or something.
Any aggressive pairs or males that interfere with others, please remove and put elsewhere for the duration as these will be your "troublemakers".
You will have to be prepared to watch closely and look for potential problem relationships.
You WILL get babies that "don't belong" to the father you thought was in fact the father, as some birds will mate with a few different partners under these circumstances. And in those cases, you may have nasty fights between the males over the chosen female.
Breeding in Breeding Cabinets or Cages
If you wish to be sure of the parentage and be able to selectively choose your pairs then it is best to breed in individual cabinets or "closed breed" ...one pair to a breeding cabinet.
Breeding cabinets reduce stresses on the parents. It means you KNOW who the father of the babies is. It IS a controlled environment.
If by any chance a mother has to end up raising her babies alone, she can do it in a breeder cabinet, where I doubt you would have a good result in colony breeding.
The thing to be sure of with breeding this way, is that the chosen cabinet is big enough for both parents and 6 to 8 fledging babies. An outside fitted nesting box is best to allow more room inside the cabinet for the parents. You need strong and stable perches for the mating act to be successful. Here are examples of breeding cabinets or cages Breeding Cage Size/Dimensions Breeding Cage Size/Dimensions