Just like all waterfowling, it depends on how much they want to be where you are, and how hard they have been hunted. As the other guys said, they are generally very willing to decoy to other species with white on the butt, especially geese or drake mallard decoys so you can supplement your brant rig with other species. We have had many great hunts with only 8 decoys, but no matter how many decoys you have it is best to find a spot they are using, kick them out, set up and they will likely be back.