Be careful what you read on the net, in the last revisions (2008) starling were granted open general license but only in Scotland and Ireland, it isnt applicable in England, therefore trapping and shooting is an offence, I dont know how you stand on disturbance
Table 1. Bird species covered by relevant general licences
Canada goose1
Jackdaw
Magpie
Rook
Carrion crow
Starling3
Woodpigeon
Feral pigeon
Collared dove2
Jay2
Lesser blackbacked
gull
Great black-backed gull
Herring gull
House sparrow3
1 England only.
2 Not applicable in Northern Ireland.
3 Not applicable in England
"In carrying out your activity your prime objective must meet at least one of
the criteria for which the relevant licence is issued, such as: conserving wild
birds, prevention and spread of disease, prevention of serious damage to
livestock, food-stuffs for livestock, crops, vegetables, fruit, growing timber,
fisheries or inland waters, preserving public health or public safety and
preserving air safety."
therefore, you would have to prove the general license was being use for preserving pulic health, dont think pooping on cars is valid reason (above info is available from basc)
also found this snippet from the telegraph online
"Volunteers from the Italian League for the Protection of Birds are using recordings of the starlings' distress call, amplified hundreds of times, to scare the flocks away and protect Rome's centuries-old statues, fountains and buildings from their noxious guano.
The sound of the distress call has been likened to a cross between fingernails dragging down a blackboard and the opening of a rusty barn door.
"We use a different cry each day," said Giovanni Albarella, coordinator of the league's starling squad. "It's all about fooling them. The trick is to make them think they are in danger."