Scarecrow

I need to hear from people that are using the "scarecrow" sprinkler to scare
off critters as to whether it really works, pros & cons. After two years of
our pond life, a heron has discovered it. We have a bird sanctuary but that
is not the bird we want and before we actually got to see it, some of our
oldest fish are gone and we are heartsick. I have the pond netted right now
but I would like to use the sprinkler if it really works. Thanks for any
comments and suggestions.
Kathy