If you have multiple birds who get along well enough to share a cage, but need lots of space of their own, you should consider a double bird cage for your flock. A double flight cage — the horizontal kind, with the divider removed — for example, would be great for a bonded pair of conures, cockatiels, lovebirds or a flock of finches. A double macaw cage would be suitable for a large pair of bonded birds or could be used as an extra large aviary-style home for a single large parrot. If choosing a stacked double cage (one cage on top of the other), please make sure the bottom cage has plenty of access to light.
Tip: Always introduce new birds to each other slowly. Don’t simply put a new bird in your existing bird’s cage. It’s very likely that two newly introduced parrots may not like each other, and if a new bird is perceived to be invading the other bird’s territory you will likely see aggression. Only allow birds to share a cage who have already shown that they are willing and eager to live together.