We recently visited the Getty Villa in Malibu, http://www.getty.edu/visit/. It's a remarkable museum of Roman and Greek art, housed in a replica of a Roman villa. The museum was built by J. Paul Getty and is funded by the foundation he established.
I was delighted to find these chickens in a still life on the wall at the top of the Outer Peristyle. The description is specific about the accompanying painting, but doesn't give anything about the chickens. I've contacted the museum to see whether they have additional information.
Dorkings are the breed still living that is most identified with ancient Rome, but certainly there were other chickens. These appear to have some small crest, so they may presage the crested breeds, such as Polish, Houdans and Crevecoeurs.
Admission to the Villa is free. Parking is $10 per car. It's an exceptional place worth a visit when you are in California.