I know a guy that used to shoot the preshow video for ESPN Outdoors years ago.
He told me about how he hunted snow geese that were sitting in fields. He took a piece of plywood about 4 x 6 feet and he would camo it with the ground material from the field he was hunting in. He would then hold it up it in front of himself and walk right up to the birds. They couldn't distinguish it from the ground and would stay put until he dropped it and started shooting.