Back in the 1970's, I made a cow silhouette decoy that we used for hunting geese in big open fields for a short period of time. It was nothing fancy, just a big piece of cardboard that I cut to the shape of a cow and roughly painted to look like one of the local bovine. It worked just fine....for a while. Two of us would hide behind it and walk out into these giant plowed fields where the geese would land. It had eye slots in the side so that we could look at the geese as we approached. The geese would ignore us for a ways, then start looking a little concerned at a hundred yards or so, and then start walking away from us as we neared shotgun range. We would try to walk just a little faster than the geese and, as I recall, we actually walked up to within shotgun range on at least one occasion. The problem with the whole deal was that the entire escapade was so funny that by the time we got within range, we were both laughing so hard that we literally could not shoot! I kid you not.
We used the method a few times just to see how it would work over time, and eventually the geese got where they were afraid of the cow silhouette (and probably all of the real cows, too). However, I suspect that it would work on turkeys, as well, if they are used to being around cows. I also suspect that it won't work more than once or twice on any given flock of birds....and probably only once! Of course, that one time is likely all you would need.
As a sidelight, we also used a cow silhouette for pronghorn hunting here in southern NM in the '80's. It would work sometimes, and sometimes not. I remember one nice buck that let us walk from half-a-mile away to within 35 yards of him. But on another occasion, a herd that was about that far took off as soon as they saw the cow. Go figure.
And finally, being my normal oblivious self, I had no idea that a person could actually sell cow silhouette decoys and make money from it. I could have done that thirty years ago! No wonder my wife's nickname for me is "Dumba$$" (among others)!