Since you asked....
Nothing short of actual physical barriers will completely deter this pestilence of the sky and water. Even then, I've seen video of these winged devils biting through a net to get to the fish in the pond.
Some of the more effective methods...
Shotgun patrol with a lot of people and guns. Steel pellets only over water. Type T or Type F work pretty good but takes practice. If incorporated along with propane cannons, fireworks, and sniper rifle, this is the best. For a large area some of the shotgun patrol will need to be on ATVs or in trucks. You can clear an area for several days this way, but if all the farms around you are doing the same thing, they'll be back. A two story sniper nest every few hundred or so acres helps.
They can be scared off pretty good if you use a combination of ATVs, hovercraft and helicopters, but it is a constant battle all day long every day and expensive. The turkeys will adjust to your schedule and show up early or late until they find a time when nobody is around.
We found that this thing called a "Scaryman" from the UK worked pretty good with propane cannons. It was like a balloon thing that would every so often blow up real big, wave its arms about, make noise, then deflate for awhile.
They'll eventually get to where the cannon doesn't even phase them if you don't "drop a few," now and again. Plus we've had those Eastern European cannons explode more than once...
If you could afford one of those specially trained dogs (roughly $15K) that patrols and scares away birds, like at airports, that works well for a small enough area.
I've had some of those nuts that play with hawks and eagles come out and an eagle chasing them away works really good, but again, too expensive for all day every day.
For cheap and fairly effective the best thing we've found is to use these "Saturn Missile Base" things you get at the fireworks stand. For cheap you can get a license to buy wholesale and you can get a truckload of those things for $100. They have like 50 or 100 shots that shoot off and go bang at the end. We'll put about ten or twelve of those on a plywood float with some fuse rope to go off every so often and that works pretty good for the money.
Until they knew what it was, scared the heck outa the neighbors. Sounds like .22 rounds ricocheting around. The "whiz bang" can sound more like "bang whiz," once it gets going.
When I had a special federal permit and 4000 acres to protect, we did all of it. Rifle, shotgun, ATV, hovercraft, helicopter, airplane, fireworks, drones, predators, dogs, etc.
When I had $millions$ of koi on 25 acres I had every pond covered with parallel monofilament lines (80-150 lb. test) on 12 inch centers. That actually worked pretty good. The birds couldn't land through the strings. But you could not have an uncovered pond by a covered one, they'd land in the unprotected pond then walk across the levee and into the protected one. We then began using bulk gill netting to make fences.
We did all we could to minimize conflicts between wildlife and our koi crop and the strings were passive, but still sometimes caught and hung predatory birds persistent enough to try.
In other states with larger aquaculture industries they just find the roosts then spray them with detergent while on the roost, then they lose their oily coat and die of exposure when it rains.