Many female cockatiels begin to lay eggs when they reach breeding age or older. This does not necessarily mean that your pet requires a mate. Often, if you have a very tame female cockatiel, she will not accept a male as she has been highly imprinted with humans. If you do purchase a mate for your cockatiel, however, make certain that you quarantine the new bird away from your pet for a minimum of 30 days (45-60 is better). During this time, schedule an appointment with your avian veterinarian for an examination. I recommend that he examine fecal samples as well as do an overall checkup. Even if he proclaims the new cockatiel as healthy, you must still follow through on the quarantine for the safety of your female, just in case!
Some cockatiel hens seem that they will never stop laying eggs. If your cockatiel is one of these incessant egg-layers, there are several things that you can do to help her. First, make sure she is getting a healthy diet. It is important that she is receiving enough calcium in her diet to replace the "reserves" she is using up creating all those eggshells. Make sure there is a fresh cuttlebone in her cage, and try to feed her foods which are high in calcium, such as collard greens, dandelion, turnip greens, kale, brocolli and mustard greens. She also needs extra protein during this time period to create the egg yolks. If your cockatiel is on a mainly pelletized diet, congratulations. If not, make sure you provide her with foods such as egg and cheese, which are both excellent sources of protein.
If your cockatiel lays her eggs off the perch (you find them cracked at the bottom of the cage), chances are she won't want to sit on them. If, however, she has stayed close to the bottom of her cage, laid her egg gently in a corner, and has snuggled down to keep it warm, don't take the egg away from her. Chances are she will only lay as many eggs as she needs to fill her "nest." After three weeks she will probably have abandoned her eggs because instinct tells her they are dead. If not, wait until she is away from them to eat or drink, and remove the eggs. At this point, if she has not stopped laying eggs, you may have a greater problem.
Often, light is the stimulus which beckons birds to breed. When the amount of light (natural or unnatural) that reaches your cockatiel's cage reaches approximately 12 hours per day, it is instinctual for her to want to reproduce. You may have to fool your cockatiel into thinking it is perpetually winter. Keep the shade drawn and keep her cage covered on three sides during the day so that you have some time with her when you come home at night. Allow her 11-12 hours of sleep at night with her cage fully covered. If she still continues to lay one egg after another, see your avian vet. He may want to give her hormonal shots, or, in extreme circumstances, remove her ovaries to prevent future problems such as thin shelled eggs and egg-binding.