When Hunting sloughs I had been using about a dozen or less, and then doing the same when switching over to flooded fields. Then, last weekend I thought, what the heck. I tried more and put out four dozen mallard decoys, no mojo, and had them working the decoys. I had enough working that I was able to even see if they would come in without using a call, and it worked. They kept coming. The only bad part to it all, is that they were all shovelers. But, at least they make good training birds for the dog.
Breeding and Training Boykin Spaniels, a True American Gundog