I'd think they might just stand on top of the fence. I have a blue heron that hangs around my pond. I've only seen him take one bluegill (I'm sure he has caught more) but he seems to take a lot of snakes, frogs and crayfish.

He looks very ungainly crashing into water after fish but suprisingly accurate - he grabbed one of my lures one time - luckily dropped it when I yelled at him. I just let him hang around.