Sex link breeding involves mating 2 different breeds in order to recognize the sex of chicks at hatching, eliminating the need for difficult vent sexing, especially challenging in tiny bantam chicks. The initial work was done by Punnet and Pease at Cambridge University in England in 1929. Their work was very useful during World War II as chicks could be sexed as day olds and male layer chickens eliminated saving scare food supplies. Such chicks possessed hybrid vigor, particularly in regards to growth rate.
There are several forms of sex-linked breeding.
1. "Gold" and "Silver" parents which produce chicks whose sex can be recognized by down color at hatching.
2. "Barred" and "Unbarred" parents where a rooster with yellow undercolorin, such as a Rhode Island Red or New Hampshire Red is crossed with a hen that has silver undercoloring such as a Barred Rock. Cockerels of such chicks have white spots on their head.
3. Parents that produce chicks with different colored shanks, the male being yellow and the female dark colore.
4. Parents producing fast feathering (wing) females and slow feathering males.
Examples of sex-linked crosses include the following:
1.Rhode Island Red male x Light Sussex female: pullet chicks are buff brown and cockerels are white or yellow.
2. Brown Leghorn male x Light Sussex female: pullet chicks have a light brown head and back with dark chocolate stripes. Cockerels are black and white.
3. Rhode Island Red male x Barred Rock female: pullet chicks are mostly black and males are colored like barred rock chicks with light colored legs and a white spot on the head.
4. Rhode Island Red male x White Wyandotte female: pullet chicks are brown with a darker stripe running down them. Cockerels are silver with dark markings.
5. Brown Leghorn male x Barred Rock female: pullet chicks are all black on top with beaks, shanks, and toes very dark or black. Cockerels are black on the top of the body with a white head spot, and beak, shanks, and toes are yellow.
6. Barnvelder male x Columbian Wyandotte female: produces results similar to the Brown Leghorn male x Light Sussex female cross.
It should be noted that these crosses involve specific male to female matings. Switching the male and female breeds around result in chicks that all look alike.
(from Exhibition Poultry Breeder's Handbook, 2nd Edition, 1997. Rick Kemp, Kangaroo Press, Australia)