Cockatiels should be at least 18 months old before you breed them. Males younger than this can be infertile and females can suffer physical complications such as egg binding. Babies can be born weak and less healthy. Do not breed cockatiels that are related to each other and have the same bloodline. Inbreeding in birds causes the same problems as inbreeding in humans. Babies can be born with birth defects and physical abnormalities such as, missing toes, deformed wings as well as problems with their internal organs. Birds that have been inbred are also more susceptible to diseases, Only breed birds that are from different bloodlines. Do not let your cockatiels breed more than 2 clutches of eggs a year. Laying more eggs than this puts a physical strain on the female's body and she can get sick. Depletion of calcium from laying too may clutches of eggs can cause seizures, egg binding as well as sudden death. Breeding season is from Spring to early Fall when  there is a longer period of sunlight each day. Your birds need to rest during the remainder of the year to build up strength for the next breeding season.

Longer daylight hours, more frequent misting with water or baths, a healthy diet that includes breeder's pellets as well as soft foods 3 months before planning to breed and the presence of a nestbox encourage birds to start breeding. Use the proper size, wooden nestbox for your breeding pairs. The size of a cockatiel nestbox is about 9"-11"-12" with a 2 and 1/4 inch opening. Each breeding pair should have their own nestbox, with 1 pair of birds per cage. Line the nestbox with a few layers of shredded, white paper towels. Make a small dent or well in the center. This is called a nest bowl and it will help to prevent the eggs from rolling around. White paper towels will give the babies a firm grip on the floor and will help to prevent splayed legs. Some birds will toss out the paper towels. My avian vet said that using a washable, disposable rubber mat can be used instead to minimize slippage. Do not use liter, corncob, walnut shells, pine or cedar chips/shavings as nesting material. The fumes from pine and cedar products and the dust they produce can cause respiratory as well as eye problems for chicks and parents. These materials, if swallowed by a chick, can also cause digestive impactions, leading to the death of a baby. Although many breeders still use pine shavings as nesting material, my avian veterinarian does not recommend them since some batches can be very dusty. Eggs laid on the bottom of the cage floor rarely hatch unless you put them in some sort of nesting container. If your birds do lay eggs on the cage floor, you can put a small bowl, basket or a  cockatiel nestbox that has been prepared with white paper towels, inside of the cage. Put the eggs inside of the nest bowl. Hopefully, the parents will start nesting on them

Eggs that are rolled around briskly or eggs that suffer trauma when parents are suddenly startled inside of the nestbox, will addle. Addle means that the contents of the eggs have been shaken or scrambled inside of the shell. When this happens in the early development of a chick, the embryos are destroyed and they will not hatch. Some people deliberately do this when they do not want eggs to hatch. If you kill a baby this way it's the same thing as a bird abortion. This is a moral issue and the decision to addle an egg rests with an individual's conscience. I personally do not agree with the practice. When embryos die of natural causes, later in their development as chicks, they are referred to as DIS, "Dead in the Shell" babies. There is a link to an article on the bottom of this page, "Eggs Not Hatching", that will provide you with some of the main causes of DIS babies. Please take the time to read it.

Eggs are laid about 7-10 days after a pair mates and 1 egg is usually laid every 48 hours until the clutch is complete. The size of the clutch can range from 2-8 eggs. You should be aware of  the symptoms of egg binding so you can get help for your female if she has trouble passing an egg. (Egg binding information can be found on a link at the bottom of this page). The female will have very large and odorous droppings during the egg laying process. She will hold it in and wait until morning to relieve herself. Sometimes the parents will not start nesting on the eggs as soon as they are laid and will wait until 2 or 3 eggs are present. The purpose of this is so that most of the eggs will hatch around the same time. Eggs do not start to incubate until they are nested on and get warm. They can stay viable for up to 7 days before nesting is needed.

You must provide a bowl of water for the birds inside of the cage. The female will wet her lower body feathers and sit on the eggs. She does this to keep the eggs moist and maintain the proper humidity level so the embryo doesn't die. Your birds will also turn the eggs once every hour during the day and some pairs will also turn them during the night. This prevents the baby from sticking to the shell and  helps organs to develop properly. If you notice eggs that are cracked you can repair them by applying a coat of white, non-toxic, water soluble glue such as Elmer's Glue. Larger cracks can be repaired by placing a piece of sterile gauze over it and then applying several coats of glue. Wait 30 minutes between applications. Repaired eggs must be watched closely during hatching. The chick may have trouble breaking through the seal and may need help during hatching. Since the glue is water soluble, use sterile water and a small paintbrush to moisten the area and carefully remove the gauze. Always wash your hands with an anti-bacterial soap and hot water whenever you handle eggs. You should also use a hand sanitizer as well. Eggs are porous and any harmful bacteria on your hands will get inside of the egg, harming the growing chick.

Both the male and female birds take turns nesting on the eggs or they nest on them together. Do not separate the pair unless one of the birds is becoming extremely aggressive towards a mate or the babies. Sometimes fights can occur between the male and female, especially during the egg laying process, but this is normal. The female may get upset if the male wants to come inside of the nestbox. This usually changes once the babies hatch. She needs the father's help to feed the babies. You may see the parents squabbling for a few minutes then cuddling and preening each other a little later. Do not remove a partner unless the partner is plucking feathers from its mate or the babies, or if it is pecking at them and they are in danger of being injured.  It's normal for the parents to be aggressive towards you when breeding. They are doing their job and protecting their eggs and babies.

Cockatiel eggs will hatch 18-21 days after actually nesting began. Candle the eggs on day 5 of nesting to see if they are fertile. Either purchase a candling light or hold a bright flashlight next to the egg in a dark room. Always wash your hands with hot soapy water and use a hand sanitizer before touching the eggs. Use extreme care in handling the eggs. Hold them level and. do not tilt, roll, shake or spin them around. Placing the eggs in a bowl of bird seed will cushion them and prevent damage when moving.  Fertile eggs will have a red, spider like shape present. There will be a dark spot in the center and you will see red veins starting to develop. There will also be a white space inside of the egg. This is the air cell. Mark each egg with a permanent, soft, felt tipped marker so you will know when to expect hatching. As the hatching date approaches, candled eggs with live chicks will appear as a large, dark mass with veins. The air cell will become larger and start to tilt. A baby will then reposition itself and move into the air cell. You may hear peeping sounds coming from inside of the egg. You will also notice a small bump with tiny cracks on the outside of the shell. This is called a pip mark. Babies have a tooth called an egg tooth which is used to crack the egg. You can expect an egg to hatch 24-72 hours after the appearance of a  pip mark. Babies push on the egg with their backs up against the shell and their little feet pushed against the opposite side of the shell. This is what cracks the eggs open so a chick can hatch. NOTE: If there is no change in appearance at the site of the original pip mark after 48 hours, the baby may need the help of an avian vet for an assisted hatch.

Babies that just hatch are usually not fed by the parents until they are 8-12 hours old and completely dry. The baby already has nutrition from absorbing the yolk sac prior to hatching. Dehydration is the most serious complication during this time. Newly hatched chicks that look red, wrinkled and thin are dehydrated. Some breeders will give the babies 1 drop of warm Pedialyte every hour to help prevent dehydration. Do not handfeed the baby with formula during this period because the crop is so tiny. It needs to be stretched out gradually. As the baby grows and starts to consume more food, the crop will stretch out by itself.