You should not start breeding cockatiels until both birds are at least 2 years old. This is the earliest that wild cockatiels start to breed. They start maturing at under a year old, but are still developing physically and emotionally. Because wild cockatiels have to learn to survive, and then find a mate, nesting site, etc., they simply are not ready to breed as early as they become sexually mature. It’s a mistake to pair up cockatiels at a younger age than 2, but some people do this. The birds are not ready. They are more likely to develop bad breeding habits that will ruin them for ever being breeders – eating or breaking eggs, not sitting on eggs, or not caring for the chicks. Once they start this, it’s nearly impossible to break these habits. A young female is also at a high risk of becoming egg bound and dying, because she simply isn’t physically developed enough to lay eggs. And young males typically only want to mate, so they get bored with eggs and end up abandoning or destroying the eggs, and then they get aggressive towards the female if she doesn’t want to mate again. If you decide you want to breed your bird when he is old enough, you need to get a female about the same age. If there is too much age difference, they often will not be compatible. But you should not introduce them in the same cage until both birds are 2 years old. All cockatiels have the appearance of females when they get their feathers. When they go through their first adult molt at 6-8 months old, the males will start getting male markings. There is no way to know if cockatiels understand what sex other cockatiels are when they are young. In captivity same sex birds will bond like mates. Keep in mind that if you do breed your birds, they will no longer be pets. Breeding birds bond with each other and no longer want human companionship. So if your male is a pet and you want him to stay that way, do not get another bird and try to breed them.
Thank you for asking Lafeber,