I bought one of those Bunnings hawks to scare off Noisy Miners that attacked their own reflections in a glass door from dawn til dusk.
The Bunnings hawk was useless and became more of a launch pad than a deterrent.
We hung some shiny metallic spiral thing that glistens in the sun and twists with the wind. The farking Miners **** themselves and haven't been back.
It doesn't seem to have the same effect on pigeons though.
Worth a try with ducks.