Personally I like most follow the ALBC definition of heritage, which, is REALLY hard to achieve with hatchery stock RIR's and Ameraucanas considering A) hatchery Ameraucanas aren't real, they're mutts B) Ameraucanas weren't accepted before the 60's and C) Rhode Island Reds from hatcheries have been bred so strictly for production, so far from the dual purpose type standard, I'd say there is little chance of breeding back using purely production/hatchery stock. Sorry.
If you want to know the standard for breeds though, and you want to be serious, - I highly recommend purchasing yourself a copy of the American Standard of Perfection.
Same goes for their Barred Rocks. Extremely popular for layer/pets, so they're far from the enormous birds with square bodies you'd see at a farm who has truly old, heritage lineage. And yes, the oldest lineage out there DOES tend to follow the SOP.
Breeds of chickens these days were bred and created based out on their SOP and economic guidelines, not to be a laying hen that resembles a blurry out-dated icon of the breed or color.
If you want to know the standard for breeds though, and you want to be serious, - I highly recommend purchasing yourself a copy of the American Standard of Perfection.
Same goes for their Barred Rocks. Extremely popular for layer/pets, so they're far from the enormous birds with square bodies you'd see at a farm who has truly old, heritage lineage. And yes, the oldest lineage out there DOES tend to follow the SOP.
