Often the question of genetics is the term division. Split in birds simply means, a genetic trait and / or color that is carried, but is not visually seen.
Sometimes there may be feathers on the nape (perhaps white patches) that reveal that a bird may clearly carry some other mutation or color trait, than it appears to be visually. Or it can be something like a white nail on a particular type of bird that would normally be black.
I like to think of these as little secrets and clues to what a new color or trait might be, other than what you can actually see.
My favorites are the unexpected. When a bird seems ordinary and produces the unexpected (it breaks and is not noticed).
# 1 Example: male gray cockatoo X hen gray cockatoo = 100% all gray chicks. But if I have a Lutino chick in the nest, what does this mean? How could this happen? Well, lutino is a sex-linked gene itself, so this means that the male gray cockatiel (dad) is lutino split, and we can pronounce this lutino (girl) as a girl. Because the hen (mother) is gray.
From father to daughter, the mother hen would have to be a visual Lutino and the divided or visual father to produce a male Lutino chick. Also, half of all gray male chicks will also be split lutines, and not all hens (chicks) will be lutines, some will be gray but not split!
# 2 Example: Wear another gray pair again, if I have a white-faced chick in the nest. I know that it takes two recessive visual or non-visual white face (split) genes to make a recessive visual white face. This now means that the gray male cockatiel (dad) has a split white face! And the gray cockatoo hen (mother) also has a split white face! Therefore, this white-faced girl could be a boy or a girl. Now the brothers and sisters that are gray, about half of these will also be divided and the other half will not.
I must emphasize that this article does not include split matching!
After reviewing these tables, you will find how many genetics are similar. The blue ringneck, blue parakeet, blue quaker, Dutch blue lovebird, fallow cockatiel, multi-colored cockatiel, and white-faced cockatiel are all recessive! Lutino ring neck, lutino budgie, lutino quaker, lutino lovebird, pearl cockatiel, cinnamon cockatiel, and lutino cockatiel are linked to sex. Albino ringneck, albino budgie, albino quaker, creamino lovebird, and albino cockatiel are all “recessive and sex-linked.” And yes, you can have more than one recessive gene in a bird and a combination of recessive and multiple sexlinks, but we’ll save this for next time!