I did two things that completely solved the problem.
(1) installed bird control spikes
http://www.homedepot.com/buy/outdoors/garden-center/bird-x/plastic-spikes-kit-10-ft-8905.html
(2) installed a head rotating owl
http://www.amazon.com/Dalen-Gardeneer-SRHO-4-Solar-Rotating/dp/B005J24R26
Good luck.