What is a pineapple conure, genetically?
There is no pineapple gene. Pineapple is a trade name for a green-cheeked conure that happens to carry two separate mutations at the same time — cinnamon and yellow-sided — and almost everything that surprises people about breeding pineapples follows from that one fact. The colour calculator treats it as the two genes it actually is, which is why its answers sometimes differ from older tools.
Predictions are statistical. Percentages describe a theoretical infinite clutch, not the four eggs in front of you, and mutation names vary between breeders and countries. Why this matters more than it sounds.
The two genes underneath
Cinnamon turns black pigment brown. Markings that would be dark come out a warm coffee colour, the flight feathers are noticeably paler than a normal green-cheek's, and chicks hatch with plum-red eyes that darken over the first weeks — which is the earliest and most reliable way to spot one in the nest.
Yellow-sided — the mutation geneticists call opaline — moves melanin off the body feathering. The chest and flanks lift from green towards yellow, and the red belly patch spreads and brightens.
Put both into one bird and the effects stack: pale brown markings instead of dark ones, on a body that is mostly yellow, with a strong red front. That combination is what the hobby calls pineapple.
Both genes live on the same chromosome
Cinnamon and yellow-sided are both sex-linked — they sit on the Z chromosome. Two consequences follow, and the second one is where the interesting part is.
The first is the ordinary sex-linked behaviour: a pineapple hen gives her daughters nothing, because daughters take their only Z from their father. That article covers it in full, and it is the reason a pineapple hen paired with a plain cock produces not a single pineapple chick.
The second is that two genes on the same chromosome travel together. They are not shuffled independently the way genes on different chromosomes are. A calculator that treats cinnamon and yellow-sided as unrelated will get a whole family of pairings wrong.
Cis and trans: the same cock, two different birds
Consider a normal-looking cock who is split to both cinnamon and yellow-sided. He has two Z chromosomes, and there are two ways those genes can be arranged on them:
- Cis — both genes on one Z, the other Z carrying neither.
- Trans — one gene on each Z.
He looks exactly the same either way. There is no way to tell by eye, and his daughters are the only thing that will ever tell you. Paired with a plain green hen:
- Cis father — about a third of his daughters pineapple, about a third plain green, and the remaining third split between cinnamon and yellow-sided.
- Trans father — about a third cinnamon, about a third yellow-sided, and the rest split between pineapple and plain green.
Same two birds, same description on paper, and the nest comes out inverted.
The 32 % that most tools get wrong
The reason those thirds are not quarters or halves is that chromosomes swap segments when sperm is made. How often two genes get separated depends on how far apart they sit, and for cinnamon and yellow-sided that has been measured: they come apart roughly 32 % of the time. Taylor and Warner published the figure in 1961 and Inte Onsman confirmed it over more than a decade of test matings.
Two caveats you should have. The measurement is in budgerigars — nobody has published an equivalent for green-cheeks, so it is the best available estimate rather than a fact about this species. And the "1 to 3 %" that circulates on forums is a real number attached to the wrong pair: it belongs to cinnamon and ino, which sit very close together. Cinnamon and yellow-sided do not.
The practical upshot is worth stating plainly, because it is the case older calculators get wrong: a trans cock can absolutely father a pineapple daughter. It happens to roughly one daughter in six. Any tool that tells you it is impossible is modelling the two genes as if they were locked together permanently, and it will send you looking for an explanation for a chick that needed none.
Pineapple plus something else
Add turquoise to a pineapple and you get a turquoise pineapple — the blue-series version of the same bird, where every yellow becomes closer to white. Add the dilute gene as well and the naming stops being reliable: several combinations are sold under more than one name, one name is used for more than one combination, and a few combinations have no agreed name at all. The calculator lists which genes each trade name refers to, and says openly which ones it declines to name.
If you are buying one
Ask what the parents were, not what the bird is called. A seller who can tell you the father's colour and whether he was split to anything has given you more usable information than any name on a label, and it is the only thing that lets you predict what the bird will produce.