By no means am I an expert on this, but don' t forget to take wind direction into consideration when setting up your dekes. If the slough it 1/2 mile, there may be better spots towards the center that are holding the birds. Do you have a canoe or a boat to access these core areas? What about walking there on foot to scout it out? Maybe there is a better feeding/loafing area close by that most of the birds flock to. Just a few ideas...