There is an electronic system you can install, the name of it escapes me, however you tack up these strips wherever they like to roost etc and it works like an electric fence, It's not harmful to the birds and they learn to keep away. Rig it to a Solar collector and it'll run free all day. i dont know what it's called, I've seen it on either Dirty Jobs or Verminators.

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed