The little green heron is more agile and can get into my small pond whereas the big blue needs more space to land.
Don't be fooled by the asuumption of awkwardness. A GBH can gracefully land on a dime. No runway or landing room needed except enough space to flap his wings.
+1
I was recently fishing a small trout lake in Northern Wisconsin and observed a heron there. It perched in a tree, which I have never seen a heron do before. If a heron can land on a tree branch, I'd imagine that it can land pretty much anywhere. They can also fly incredibly slowly, really taking their time to look for a good spot.
I wonder how difficult it would be to rig up a float rapala (de-hooked) to some line and an alarm. Somthing like this, for herons:
http://www.youtube.com/watch?v=6aYDWf5JKYoOr make one of these, if there is only a small area suitable for herons and you have a water line at the pond:
http://www.youtube.com/watch?v=gdYc86AA8M0