Article: Typically, putting cockatiels of the same sex together in a cage together works well if they have gotten along during initial meetings. However, to avoid potential territorial behavior, consider getting a new cage that is big enough for both birds and have them both move into it at the same time. With enough space and a neutral territory to begin with, the stage is set for them to live peacefully together.  If you go for the option of a new and 'neutral' cage, make sure all the fixtures and fittings, such as toys and food bowls, are new so that the birds don't defend property that was once theirs. If you put male and female cockatiels together they may get along, but you will likely end up with baby cockatiels. Sometimes when you have multiple birds it is easiest to just keep them in different cages forever. This will ensure that they each have enough space and that they each get all the food, water, and access to toys that they need. It will also help ensure that they do not become aggressive or territorial with one another. Keeping birds in separate cages doesn't mean that they won't interact with each other. You can put the cages next to each other and you can let them out of their cages at the same time, if you like. If you have birds that are aggressive towards each other, even when kept in separate cages, then you will need to keep their cages far away from each other. If they stop aggressive behavior when the cages are separated by a few feet, then move them to opposite sides of the same room. However, in severe cases, you may need to keep them in separate rooms altogether. It is better to keep birds that don't like each other out of sight of each other than to hope that they will eventually get used to each other. The stress of aggression and fear can impact the bird's health and attitude towards you as well.
What is a summary of what this article is about?
Put cockatiels together in the same cage only if they get along. Consider keeping your birds in separate cages permanently. Separate birds that don't get along.