An option could be to select an open area to setup in,place a fresh road kill or something that is in season like a squirrel.
Rip it open a little, as when they get closerI believe they can smell it.
Sometimes many birds will come into your setup and your golden.
However, I've found that if a single bird will come into your call or setup, let him leave.
As he is a searching bird and will usually bring in more birds soon, meaning more chances!!!
Although, it could be a lone bird and if this is the case let him eat for 10-15 minutes remaining perfectly motionless.
If no other birds find him, let him have it.
You could also try 1 decoy, as this can indicate a loner and may be spotted by a group and entice them in.

Just be ready, as you may have a fox or yotecome and visit!!!

Good luck and remember they are very tough birds, so go with your Duck loads, say #4's