Breeding...
Breeding scarlets is easy enough if you have the right facilities. You want to purchase young, healthy birds. Avoid buying older pairs unless you can see them in person. In the case of any bird, if you don’t like the looks of the bird OR its environment – Don’t buy it! Keep all new birds away from your current birds for at least 1 month (ideally 3 months) to prevent spreading diseases (you can’t always tell an unhealthy bird) and to be able to monitor the new birds closely.
Scarlets will begin breeding at around 18 months. A standard parakeet box should be fine though you may need to widen the hole a bit. You don’t want something too big though or they won’t feel secure. I get mine off ebay with 3 doors (top, and 2 sides) and attach it to the outside of the cage for better access and to give them more usable space inside the cage.
They will court by feeding each other and the male will bob up and down. He will go to the nest box and look around. The female, when she is ready, will go in the box and spend a lot of time “housekeeping” for about a week before she is ready to breed. I use EcoBedding, a shredded paper bedding. Avoid shavings. Its not unusual for them to push out most, to all, of the bedding. Avoid disturbing the nest during breeding, once startled scarlets, especially young pairs, may not come back. It may only take once and you have lost the entire clutch.
When my birds are breeding I add in Quicko egg food. I also offer crushed oyster shell for extra calcium (tractor supply store for chickens). They need the extra nutrients for the eggs. I continue to offer them until the babies are all weaned.
She will lay usually 1 egg every other day and start incubating after the third egg. An average clutch is 4-6 eggs. If you are able to peak in and see the eggs, you will notice freshly laid eggs have a creamy peach color to them. As they develop the eggs turn a dull white and become a pale grey color just before hatching. It takes about 21 days to incubate and once they start to hatch you will hear a lot of high pitched peeping coming from the box.
Babies should be banded with a permanent number band about 10 days after hatching (approximately 18 grams in weight). Be very careful handling the legs, they are easily broken. Your bands should come with instructions on how to put them on. When in doubt, ask before doing. Birds must be closed banded with a registered number to be legally sold in most states, including New York. You may color band them as well for easier identification in the cage and to track family lines.
Babies fledge about 14 days after hatching when most of their feathers have come in. They will wean around 6-8 weeks old. Watch carefully to make sure they are truly eating on their own before removing them and then watch them carefully for at least a week after to make sure they continue to eat well on their own.
Parents may start courting again even before the babies are fully weaned. Scarlets have the potential to have 3 clutches a year, but it is not healthy or safe for them to have more than 2 average clutches a year. Hens can lay eggs without a male present. Overlaying, poor health and/or lack of calcium in hens can lead to serious egg related problems and even death. If you suspect your hen has problems she should see a vet immediately and you will be advised how to try to stop laying and increase calcium.
Allowing your birds a good break between clutches will keep your birds healthy and happy. Babies should not be sold until they are fully weaned and on their own, unless the person buying has experience in hand feeding. They should not be shipped until they are 4 months old, its just too stressful. Follow the requirements of the airline to provide the safest cage/crate for traveling. The 2 main airlines that transport birds are Delta and United (formally Continental). Always check on the day of flight your entire flight schedule including all layovers and transfers both for shipping and for receiving.
Mules ... The reason I mention this is to make owners of multiple breeds aware of something many breeders will never tell you, and only in disgust. The Scarlet, the Elegant and the Turquoisine can interbreed. I have read a few accounts of Bourkes also interbreeding but most sources say "no" they will only breed with another Bourke. The resulting offspring of the above birds are sterile or infertile and often referred to as mules. Most hard-core good breeders do not believe in creating mules because they serve no purpose in perpetuating bloodlines. The goal of these breeders is to create offspring that are superior to their parents and to continue to pass along their genetics from one generation to the next, enhancing each generation through careful selection of these superior offspring. There is absolutely nothing wrong with this goal and belief.
I am not a hard-core breeder. I believe each person who wishes to get into breeding look at their program and decide what goal they wish to have. You could simply aim to have 2 beautiful birds that periodically produce offspring or you could decide to breed hundreds to develop a new color or mutation. If you wish to create mules for pets that is your choice, but if you do- make sure those buying your birds know what it is they are buying so they can make an informed decision for their "program's goal".