Oh! I did not know that, thanks!There are at least four genes for feather-legged. two for feathers on the shanks only, one of which causes crow wings as in Sultans, one for feathers on the shanks and toes, and one for long feathers. Most feather-legged birds have at least two of these. Some such as Cochin have three. This could be a mutation (a fifth gene for feather-legged) or could be a repressed gene that had been present, but because of the cros,s came to the forefront.