I could see where other birds could take their place as they are territorial. Steep banks definitely help. My trout pond is so steep they won't even consider it. It also has #4L stones on the banks which I do not believe they care to wade on either. However it is very close to the house so that may have something to do with it.
The warmwater pond is not so lucky although the banks are fairly steep also. However I will be fixing that this spring. Can't wait to see my first heron walk into a hot wire. Yee Haw! I've heard it looks something like break dancing.
