If you want a pet bird, then a single bird is best. When you have two birds sharing a cage, even if they are the same sex, they will bond with each other and almost always stop wanting interaction with people. A bonded pair is unlikely to be tame at all. Pet parrot behavior is driven by their natural instincts, because they are still a wild species. Young parrots in the wild interact with other flock members. When they are mature, they choose a mate and once they are bonded, the other flock members are now seen as rivals. When nesting, the bonded pairs distance themselves from the flock and any young flock members that venture too close will be chased away. If the rival won’t leave, the male will often turn on the female and attack her to drive her back to the nest or away from the rival. If you have a pet bird, you are replacing another bird as the companion. If you add another bird, this can eventually lead to biting you and fighting with each other. It can create a lot of confusion for the birds because they are torn between whether to like each other or you. It tends to work out at first, but once the birds get old enough, the trouble starts. It doesn’t mean you can’t have more than one bird, but each bird needs its own cage. And as they get older, you may need to play with each bird separately. But there are many single bird households and as long as they have toys and ideally some foraging activities to keep the busy during the day, they do fine. Some like having music or TV on during the day.
As for the outdoor aviary, this is not necessarily the best plan. Unless you live where the climate is mild year round, then much of the year it will be too hot or too cold for the bird to be outside. It’s not good to have a significant temperature change for a pet bird. If it’s 70 indoors and 50 or 90 outdoors, this can make the bird sick. They need gradual changes, not a sudden drop or increase in temperature. There are also a lot of risks to outdoor birds – parasites and diseases from wild birds and danger from predators. Everything from snakes to birds of prey, rats, raccoons, and feral or pet cats & dogs will kill a parrot if they can get hold of it. Generally a pet bird should only be outdoors when you can supervise them. Some people do keep pet birds outdoors, but you need to be aware of the risks. Most outdoor parrots are breeders, and then they still face the same risks. An outdoor aviary should have a double entry to prevent accidental escape, and the bird should be in a small cage or carrier while being transported to and from the outdoor cage.
Thank you for asking Lafeber,