Auto-sexing

Auto-sexing

The importance that auto-sexing plays in the Legbar breed is also reflected in the fact that, next to a standards for the adult birds, the down colour and patterns are also standardised.[5] Day-old male chicks can be distinguished from day-old female chicks by the down colour and the pattern they form. Female Legbar chicks in general have a broad very dark brown stripe extending over the head, neck and rump and a clear eye barring. The edges of the stripe are clearly defined and should not be blurred and blending with the ground colour, which is dark brown. A light head spot should be visible but is usually small. The male Legbar chicks in contrast have a much paler down shade and the pattern is blurred and washed out from head to rump.^[5]

The marked difference between male and female chicks is due to gene dosage of the sex-linked barring gene ('barring' (B), 'nonbarring' (b+)).

• the Brockbar, created in 1940 from buff and barred Plymouth Rocks, became extinct by about 1950[1]^: 54
• the Brussbar, created in 1952 from light
  Sussex, brown Sussex and barred Plymouth Rocks^[1]
  ^: 55
• the Dorbar, an auto-sexing heavy meat breed from
  Dorkings and barred Plymouth Rocks, bred from 1941 to about 1949, when development stopped^[1]
  ^: 59
• the Rhodebar, from Rhode Island Reds and barred Plymouth Rocks, standardised in Britain in 1951; a similar cross-breed was developed in Canada^[1]: 63
• the Welbar, not created at Cambridge but by a Devon breeder, from
  Welsumer and barred Plymouth Rocks;^[1]
  ^: 65 and
• the Wybar, also not created at Cambridge but by an individual breeder, from Wyandotte, Brussbar and barred Plymouth Rocks.^[1]: 68

Many other breeds were created in the same way, all making use of barred Plymouth Rocks to impart the barred gene:

• The American
  California Grey was bred in the 1930s in Modesto, California.^[8]
  ^: 432
• In about 1936 Arend L. Hagedoorn introduced the barred gene to Barnevelders and to brown Leghorns.^[9]: 210
• In 1940 R. George Jaap produced the Oklabar by crossing dark Cornish with barred Plymouth Rocks.^{[9]: 210 [10]}
• By 1941 the Ancobar had been bred from mottled
  Anconas and barred Plymouth Rocks, by W. F. Lamoreux at Cornell University in Ithaca, New York.^{[9]: 211 [11]}
• The Polbar was created between 1946 and 1954 by Laura Kaufman, who crossed the native Polish Green-legged Partridge breed with barred Plymouth Rocks.^[12]: 556
• The German
  Welsumer and barred Plymouth Rocks.^[13]
  ^: 6