Before you get another bird, you need to make sure your birds are not compatible. You said they are the same age, but are they at least two years old? Cockatiels really should not be breeding until they are at least 2 years old. Some birds will mature more quickly than others, and in captivity, they often are sexually mature at too young of an age. They need more time to finish maturing physically and emotionally. If your birds are under two, or barely two, I would give them a few more months. I would separate them and keep the cages side by side, and see if the male becomes more interested in the female while they get a bit older.
If these birds are two years or older, then if you do get a third bird, you can NOT put it in the cage with the other two. It needs to be at least two years old. You first need to quarantine it in a different room for about 45 days, to make sure it doesn’t have any diseases. If you plan to keep all three birds, you will need three cages to begin with. You need to separate the pair, and then put the new bird in a cage next to the opposite sex. They should be kept side by side until you see them sitting next to each other and showing interest in each other. Then you can try putting them in the same cage, but you need to supervise them closely. Birds need time to form a pair bond, and not all birds are compatible. But their chances of getting along are better if they are both about the same age, and old enough for breeding. Do not ever keep an odd number of adult birds in the same cage. Birds will pair off, even if they are the same sex, and the odd birds gets picked on or attacked. You also can only have one pair in a cage for breeding. Never give birds a nest box if you have more than two birds in a cage. It will cause fighting – cockatiels can be very territorial and aggressive towards each other, and they can quickly kill another bird.
Before you set your birds up for breeding, they need to be on a balanced diet such as pellets or our foraging foods. A loose seed mix will not provide the nutrition they need. You should also offer dark leafy greens, chopped veggies and some fruit. Once you have given them a nest box, you need to start feeding them an egg food. You can buy a commercial egg food or just cook an egg with the shell washed, crushed and cooked with the eggs. You should feed this to them until all chicks are weaned. Once chicks leave the nest box, you have to remove the box and rest your pair for 6 months. You should only allow them to have two clutches per year, which is one more than they would have in the wild. Weaned chicks have to be removed – they can’t stay with the parents. Otherwise the parents will try to breed with them. You should never keep opposite sex chicks together – never let related birds breed. Breeding birds take a lot of work and patience, and sometimes you can do everything right and still not get any chicks. All you can do it keep trying and hope you get a pair that will be good breeders.
Thank you for asking Lafeber,