I’m sorry you are having this experience. Unfortunately, this is the most likely scenario when offspring are not kept separate from the parents or siblings, once they are weaned. The short answer is, the solution that will most likely work is for the offspring to be caged in same sex pairings, with no odd numbers. To better understand this, let me explain wild parrot flock behavior. Most birds, including parrot species, live in flocks for protection. Young birds will interact as they grow and mature, and they learn from each other as well as from adult flock members. Once they are mature, they choose mates and no longer have much if any physical contact with other flock members. Their habitat is nearly endless, so squabbles are settled by distance. Flocks will have a large territory and move throughout it based on the seasons and food availability. During breeding season, pairs establish a territory and find a nesting site. Any flock member that ventures too close will be considered a rival and chased away. Juvenile flock members likely stay in a different area as a flock, as they will not be welcomed anywhere near a nesting pair. Once the chicks have been fully weaned, they will either be driven away or left by the parents. This is nature’s way of preventing inbreeding, which is when related birds breed. Inbreeding is very bad for the gene pool, so adults will not tolerate a weaned juvenile in their territory for very long.
Captive bred parrots still have wild instincts, even if they do not always understand them. When you breed birds, it is usually best to find homes for each chick. Chicks should always be separated from the parents as soon as they are weaned or one of several scenarios will take place. Most often, the parents will start picking on the offspring in an effort to drive them away. If they are caged together, the chicks have no place to go and often the parents start aggressive attacks that can be fatal. If the parents allow the offspring to stay around, which is what happened in your case, the offspring will eventually become sexually mature and either want to breed with one of the parents or with one of the siblings. Even without nests or nest boxes, they will start to fight over territory or mates. Your male offspring likely wanted to mate with his mother, and when she wasn’t receptive, he turned on her and attacked her. Her mate likely wanted to defend her, but was chased by the younger bird.
When you do keep adult chicks, they should be kept singly in separate cages, or in even numbers of the same sex, as I mentioned above. Odd numbers rarely work out, and male & female offspring will want to mate with each other if not separated. If you still want to keep all of these birds, I would recommend having all of the offspring DNA sexed, and then cage them by gender. If you have an odd number of one sex, you will have a lone bird. Same sex birds will often pair off just like a male/female pair and will soon bully any odd birds. Caging them by sex only serves to reduce some of the mating behavior and prevent inbreeding. But a same sex pair can bond like a male/female pair, and try to mate with each other, and even try to nest.
I know this is all very confusing and distressing. You see videos of odd pairings or different species all living together in harmony and it looks like everyone is happy. But these situations are either the rare exception, or young birds that haven’t reached sexual maturity yet. Many owners end up facing the same thing you are facing, because almost always, once birds do become sexually mature, the trouble starts and the happy flock is broken into birds fighting and bullying each other. This is just instinct and you can’t go against nature. This isn’t something that can be resolved by a trainer or behaviorist, because this is natural behavior. Captive raised parrots, even hybrids and mutations, are the equivalent of any captive raised wild animal – tigers, bears, wolves, etc. These are not domesticated animals and parrots are only common as pets because they don’t pose the risk to human life that wild mammals do. But they still have wild instincts and urges that have been bred out of or greatly suppressed in the domestic dog and cat, for example. And when the instincts do surface, it can be trained out of a domesticated animal because the domesticated behaviors are stronger.
I know I have given you a lot to think about. If you do keep all of them, they can still most likely interact outside of their cages, with supervision of course. Should you decide to rehome any of them, do not rehome opposite sex birds to the same home or if you sell them to a breeder, the breeder needs to know these are not pure species and that the birds are all related. Sadly, the Green Cheek conures in the US have been badly inbred to achieve all of the new mutations, just as Americans did with the Australian parakeet. So this means many have genetic flaws or weaknesses and the species is not as hardy as a whole. But they do make sweet pets and are probably one of the better choices as a family pet.
Thank you for asking Lafeber,