Often in question about genetics, is the term split. Split in birds simply means, a genetic trait and or color that is carried, but not visually seen.
Sometimes there can be feathers on the nape of the neck (white patches maybe) revealing that a bird may clearly be carry some other color mutation or trait, than what it visually appears to be. Or it can be something like a white toe nail on a particular type of bird which would ordinarily be black.
I like to think of these as little secrets and clues to what could be a new color or trait, other than what actually can be seen.
My favorite are the unexpected. When a bird looks ordinary and produces the unexpected (is split and you can not tell).
#1 Example: Gray cockatiel male X gray cockatiel hen = 100% all gray chicks. But if I get a lutino chick in the nest, what does this mean? How could this have happened? Well, lutino is a sex linked gene in it’s self so this means gray male cockatiel (dad) is split lutino, and we can pronounce this lutino (chick) a girl. Because the hen (mother) is gray.
Father to daughter, mother hen would have to be a visual lutino and father split or visual to produce a male lutino chick. Also half of all the gray male chicks will also be split lutino, and not all hens (girl chicks) will be lutino some will be gray but not split!
#2 Example: Using another gray pair again, if I get a white face chick in the nest. I know it takes two recessive white face genes visual or not visual (split) to make one recessive visual white face. This now means gray male cockatiel (dad) is split white face! And gray cockatiel hen (mother) is also split white face! Thus this white face chick could be a boy or a girl. Now brothers and sisters that are gray about half of these will also be splits and half not.
I must emphasize this article does not include the pairing of splits!
After going over these charts you will find how similar many genetics are. Blue ringneck, blue budgie, blue quaker, dutch blue lovebird, fallow cockatiel, pied cockatiel, and white face cockatiel are all recessive! Lutino ring neck, lutino budgie, lutino quaker, lutino lovebird, pearl cockatiel, cinnamon cockatiel, and lutino cockatiel are all sex linked! Albino ringneck, albino budgie, albino quaker, creamino lovebird, and albino cockatiel are all “Recessive & Sex linked.” And yes, you can have more than one recessive gene on one bird and a combination of recessive and multiple sexlinked, but we’ll save this for next time!