How to Keep Multiple Cockatiels
If you are going to buy multiple cockatiels, keep the birds in individual cages next to each other to let them get to know each other without the risk of them becoming territorial. If they seem to be getting along in their separate cages, take the birds to a neutral location away from their cages to let them meet face to face. When they are ready to live together, consider buying a bigger cage that they can fit in more comfortably. If you do get a new 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. Alternatively, you might consider keeping them in separate cages permanently, especially if the birds don't get along.
Ensure that birds are disease-free. Before you put multiple cockatiels in the same home, you should make sure that they are all disease-free. Do not allow them to have contact with each other right away, and have all incoming birds assessed by a veterinarian before they share space with your existing birds. You should try to quarantine a new bird in your home for 30 days before introducing it to your other birds. A healthy bird should be generally alert, should have well cared for feathers and clear eyes, and should not have discharge coming from the eyes or nares. Introduce your birds to each other when they are young, if possible. Younger birds can typically adjust to life with other birds more easily than older birds that have been raised away from other birds. If you have a young bird and you are contemplating adding another bird to your flock, do it sooner rather than later. However, young birds that are raised together will always be more focused on each other than on you. They will likely form a strong bond that lasts their whole lives. Keep the birds in individual cages at first. It is important to let the birds adjust to each other before attempting to put them into a cage together. Allowing them to get to know each other while they each have their own cage will let you assess whether the birds have the personalities to be able to coexist together. Placing the bird's cages next to each other will allow them to get to know each other without the risk of one or both of them becoming territorial. Introduce the birds outside of their cages. A cockatiel's cage is its special safe place, so they can be territorial when a new bird is introduced into their space. To make sure your bird's first contact without bars between them goes more smoothly, take both birds to a neutral location and let them meet face to face away from their cages. The key is to minimize any chance of friction or aggression when the birds are first meeting each other, so that they can get to know each other peacefully. This meeting must be supervised so that you can move them away from each other if they do not get along. Put cockatiels together in the same cage only if they get along. 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. Consider keeping your birds in separate cages permanently. 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. Separate birds that don't get along. 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. Provide for all of your birds' basic needs. All birds need to be provided with food , water, and mental stimulation. Cockatiels are typically mentally stimulated when they are given a variety of toys, such as bells, mirrors, chewing toys, and swings. Each of your birds should have access to food, water, and stimulation at all times. If you have multiple birds in one cage, then you need to have multiple food and water dishes in that cage. You should also put a wide variety of toys in the cage. Set aside more time for bird-related chores. Having multiple cockatiels will increase the amount of time it takes to properly care for them. You will need to spend more quality time with your pets, but you will also need to spend more time cleaning cages and changing out food and water dishes. Even if you have multiple birds in the same cage, that cage will get dirtier quicker. It will require more frequent cleaning than it did with only one bird. Spend quality time with all of your birds. When you have multiple birds, it's important that you give each of them some focused time. Take each of them out of their cages on a regular basis and take the time to train and socialize all of them, so that all of your birds continue to be healthy and happy pets. It is a good idea to make a schedule for when you hang out with each bird so that they all get equal attention. One-sided attention can make some birds jealous and aggressive towards you over time. Be prepared for a change in your bird's interest in you. When you only have one cockatiel, it will likely focus all of its attention on you. It may sing or whistle at you and it may like to spend time sitting on your hand or your shoulder. However, if you introduce a new bird into your home, then your first bird might give a lot of attention to your new bird. This is totally normal behavior that may or may not occur with the addition of new birds, but you should prepare yourself for that change. The downside of a change in interest in you is typically outweighed by the benefit that your bird will receive by being able to interact with another bird all of the time. They can give each other more interaction and attention than a human typically has time to provide. Care for the health of all of your birds. While cockatiels tend to be relatively hardy birds, they do need to get regular veterinary care to ensure that they stay healthy. Take all your birds in for an annual exam and assess them regularly for signs of ill health. When assessing the health of your birds, look at the clarity of their eyes, the state of their feathers, their energy level, and look for any changes in behavior. 
Ensure that birds are disease-free. Introduce your birds to each other when they are young, if possible. Keep the birds in individual cages at first. Introduce the birds outside of their cages. 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. Provide for all of your birds' basic needs. Set aside more time for bird-related chores. Spend quality time with all of your birds. Be prepared for a change in your bird's interest in you. Care for the health of all of your birds. 