Pigeon and Starling Problem
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Both of those birds can cause a lot of heartache but the starlings seem to be the most persistent. Because you have open spaces and not holes you can't block, I would try the following:
If you are inadvertently providing them with a food source take that away. Chicken feed comes to mind.
A hawk decoy can help keep birds away but for it to be effective you will need to move it to a new location every day or so, otherwise the starlings will catch on
Depending on how close your neighbors are, you could try noise abatement. Hazing them often with loud noise may drive them away.
With large open spaces, bird netting can be highly effective.
Here is some additional information from the Washington Department of Fish & Wildlife: http://wdfw.wa.gov/living/starlings.html