Having bred domesticated Mallards for over a decade we do NOT mark our birds in any way. Domestic Mallards differ considerably from the wild Mallard, and while we have been very lucky to finally obtain a fair number of grays that are far more streamlined and wild looking, they still have a little more domestic duck attitude than the wild ones on the pond. We also breed them in Snowy so there is no need to mark those either. You won't have any issues with the ducklings from TSC, they are sold as domestic and are for all intents and purposes domestic birds, some may fly off if left to their own devices, but the majority of them will act no different than the white Pekins. They all learn when its time to be fed and will happily come for their food.