Barred vs. Cuckoo

[WildernessLofts]

What is the genetic difference between these phenotypes? Are they completely separate, alleles, or just different expressions of the same gene?

 

[Krys109uk]

Different expressions of the barring gene.
Rapid feathering tends to give the more blurred look of the cuckoo colour. Modifiers help give the beautiful precise barring of the exhibition barred rock.