We have electric wire around all of our pheasant and partridge pens. We use either a single or double strand of wire set about six inches above the ground (the lower wire), connected to a fencing unit and a battery. As said, the long grass or anything (other than metal) touching it will reduce the voltage, so we strim and then spray off the area beneath the wire before connecting it. Any metal touching it will cause a dead short.
For some reason the birds dont seem to get electricuted, despite walking into it, and bouncing off it lots of times, they dont seem to recieve a shock? Not sure why, maybe their feathers??? The fences range up to about 7/8000 volts, and usually does the trick when foxy or brock comes calling!
I've whacked myself on the fences a few times and its not pleasant!!!!