A cheap scare tactic to keep away Herons, Owls, hawks, eagles and pretty much any predatory bird. Tie two to four CD's to a fishing line with a small weight at the end. point a solar powered light in the direction on the hanging CD's. the reflection helps scare off most birds of that type. It will however scare some smaller birds off too. I have noticed far less hiummingbirds and wrens since I installed these. I found a solar led spot light (which helps scare at night really well!) at walmart for $10, four used CD's for free, 3' of fishing string I grabbed off of my fishing pole and a small nut for weight. It may not be 100% effective but I haven't had any more cranes stealing fish since I did this.
I guess I also must mention that after $1000 worth of fish got eaten in a two week period at Christmas I have done the CD's, A PVC with wire mesh to place over the pond, a plastic blue Heron that I move every two to three days, and the water motion scare crow which I hate due to the fact I always forget when it is on and I end up getting sprayed or I forget and to turn it on after working in the yard which does no good when your away from the area not knowing it isn't working. (stinks getting old and forgetfull) I had black netting over my pond before the heron started eating fish. that bird was smart enough to stand in the middle of the net, grab the fish and pull the fish out the side thru the rocks. Folks I'm talking 3#-5# 12"-16" Koi! Not just the little guys!