For save those genes .....mutation like that happen like 1 in a million. Crest ducks ,Crest geese, even crest parakeets.
Know to breed him/her mate back to mother or father,(best) or brother or sister...i would also keep,its brothers and sisters mating them together, or if you sell them ,let the person getting them what they have....
Now people who find new mutation ,be it color or something else......those first few years the birds will sell for alot more .seen it many time maybe even 10 times as much.
The snow flake bob white quail . new mutation. their eggs where selling on e-bay for over a 100.00 per dozen or 2.
Good luck with it.