2 feet of stove pipe has been enough to keep predators out. I have mine about 10-12 feet off the ground. They will nest in trees and boxes that are well away from the water. I had one box that was originally on a tree along a little waterway that led down to the river. One year we had a drought and they still used it. When the fledglings finally jumped, mom gathered them up and took them to water about 300 yds away. Also, they are not territorial and will nest in boxes that are near each other and even attached to the same tree
