Tough problem. If you are sure they are starlings, then you can be aggressive in their control, as they are not a native species and are not protected. I had a BB gun as a kid.
Some people put up owl decoys, with mixed success.
There are two companies that make bird deterrent products. I have never used any off their products so can not comment on how effective they are or if they are environmental friendly. Some options use sound, but are fairly expensive.
http://birdbgone.comhttp://www.bird-x.comGood luck.