I know mine can get over a 4' fence when properly motivated. I have a 4' fence dividing the back yard from the front. They generally stay in the back except that my compost bin is by the fence and they LOVE to fly up to check that out. And from there it is ony about 6 more inches to clear the fence. Once on the wrong side of the fence they seem to forget how to fly and pace back and forth looking for the hole to get to the back yard (which doesn't exist until I open a gate).