Cecil I bought a couple of those plastic alligators that Zep had mentioned, and they've actually worked well. I stuck them in the shallow part of my brood pond where my BG spawn, and not a footprint or sign of any creature.
I just used decoy weights, and let them float in about a 20' radius, and even varmints are avoiding the area. Time will tell, but so far they've been great.
I wonder if it would work on a bird that is too far north to know what a gator is?
It'd be a fun project to build one with a jointed tail with an attached hose and pump to get it to swim back and forth like a water hose that is running and snaking back and forth in the water. You could put it on a timer to shut off randomly to make it more natural.
The ultimate would be motion activated sensor to get it to move close to anything that moves. Then a secondary sensor that causes it's mouth to open when it gets close to what activated it's sensor.
