Stuart Timms
Registered
my suggestion would be this, get yourself a small compressor like the ones for air brushes, then plumb in a series of lines around the garden with valves that operate via an electrical switch, then operate these valves to release a jet of air, the noise of the air escaping should scare them if the jet is at good pressure, you then have the option of positioning the jets near the areas the pigeons wander and can operate your system from the comfort of your house.