"Telling Cockerels from Pullets at Hatch: Sex-Linked Crosses"
Vent sexing day-old chicks takes a trained eye. But with the right pairing you can read a chick’s sex straight off its down or wing feathers the moment it hatches, no skill required. These are sex-linked crosses, and the genetics are simpler than they look.
A quick word on chicken sex chromosomes
Chickens use a Z/W system, the mirror image of mammals. A cock is ZZ (two Z chromosomes), a hen is ZW. A few useful traits sit on the Z chromosome, so they pass down a predictable path:
- A son gets one Z from his dam and one from his sire.
- A daughter gets her single Z from her sire (her W comes from the dam).
The trick to auto-sexing: when the dam carries a dominant Z-linked trait and the sire is pure for the recessive version, the sons show the dam’s trait and the daughters show the sire’s. Different look, sorted at hatch.
Color sexing (the Red Star cross)
Cross a silver hen (white or light down) with a gold rooster (red or buff, such as a Rhode Island Red or New Hampshire) and you get:
- Cockerels: silver / pale down
- Pullets: gold / reddish down
These hybrids are sold as Red Star, Golden Comet, Cinnamon Queen, and ISA Brown. Note the direction matters: a gold hen over a silver cock makes every chick come out silver, with no way to sex them.
Barring (the Black Sex Link cross)
Cross a barred hen (like a Barred Plymouth Rock) with a non-barred rooster (Rhode Island Red, New Hampshire) and:
- Cockerels: get the barring gene from their dam, hatch black with a white head spot
- Pullets: hatch solid black, no spot
That is the classic Black Sex Link / Black Star.
Feather sexing
Cross a slow-feathering hen with a rapid-feathering rooster and the chicks sort by wing feathers at hatch: pullets show longer primary flight feathers, cockerels shorter. Hatcheries use this widely.
Plan an auto-sexing pairing before you set eggs
You do not have to memorize which cross does what. Record each bird’s sex-linked genes in ChickenAncestry, and the test-mating tool tells you whether a given cock and hen will produce auto-sexable chicks, and what cockerels versus pullets will look like, before you set a single egg.
Curious how the rest of the test-mating tool works? See the coefficient of inbreeding, then try a test mating free.
ChickenAncestry tracks every bird's sire and dam, draws the pedigree, and computes inbreeding (COI), free to start.
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