Worries on the Line

Duck keepers are always concerned about duck safety.  Some things you can't control, some you can, some you hope for the best.

Ducks love to thrust their beaks into the dirt and hunt for bugs and worms.  I don't worry much about stale worms or even how the ducks are trashing the lawn.  I do worry about predators.  Fences keep the ducks from wandering into the tall grass or woods to be taken out by a fisher or fox.  Locking them in a sturdy house at night keeps the raccoons and other nocturnal riffraff from getting to them.

Sounds good.  But what about danger from above?  The house keeps owls away at night but what about diurnal birds of prey?

I've tried netting.  It's the stuff you use over blue berry bushes to keep the birds from eating all the berries.  Trouble is, the netting twisted and tore every time it had to be moved.  Then I read (I think in Grit magazine) something that an old chicken farmer has been using for years. He runs a few strands of fishing line from the bird house to the fence in a sort of  sliced pie configuration.  The theory is that raptors, with their keen eyesight, see the strands and avoid them.

Dipping into my tackle box, I rigged up a multi line gizmo and set it up. 

I worry though.  How do we know if it works?