Sex-links^[1] are crossbred chickens whose color at hatching is differentiated by sex, thus making chick sexing an easier process. Sex-links come in several varieties. As hybrids of laying or dual-purpose breeds infused with extra vigor via heterosis, sex-links can be extremely good egg-layers which often produce 300 eggs a year or more depending on the quality of care and feed. The color of their eggs vary according to the mix of breeds, and blue-green eggs are possible.

Chicks of a single breed that are similarly sex-linked are called autosex chickens, a term developed to differentiate between sex linkage in purebred chickens versus sex linkage in crossbreeds.

Many common varieties are known as the black sex-link (also called black stars) and the red sex-link (also called red stars).^[2] More specific variety names are common as well.

• Black sex-link like "Black rocks" are a cross between unique specially bred hybrid strains of Rhode Island Red rooster (but any non-white and non barred rooster may be used for other black sex-link crosses) and a Barred Rock hen (which carry both extended black and barring genes).
• Red sex-links are a cross between a Rhode Island Red or New Hampshire rooster and a White Rock (This variety pair is known as a Golden Comet), Silver Laced Wyandotte, Rhode Island White, or Delaware hen.

Examples of a red-linked breeds include the Red Shaver and ISA Brown sex-links which are found in Canada.^[3]

White birds should not be used in sex-linked crosses because white colour allele is sometimes dominant and sometimes recessive.^[4]

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  A red sex-link rooster
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  A Black Rock hen
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  A red sex-link pullet
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  A black sex-link rooster
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  Shipped pullets
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  Red sex-link hen
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  Black sex-link rooster

• ZW sex-determination system
• List of chicken breeds