I think most great “duck” dogs are essentially very good marking dogs to begin with. There is no difference in marking in a field trial vs a duck blind. Any great field dog will make a great duck dog when they realize what they are there for. No duck do will ever learn to run run a blind in a “duck blind” that’s learned in the field training. For people to say that blinds are not necessary in duck hunting situations is crazy. YES you need a whistle to send a dog on a blind retrieve but the whole purpose is to put them in the scent cone not on the duck. To think that a dog can pick up every duck from a blind and not handle is ridiculous.