We moved our Catalina 30 to a new marina last year and this summer the forward deck was covered in poop. Reading the archives and other sites, I tried hanging CD's (two glued together shiny side out) on the life lines. We went on vacation for a week and behold no poop. Dig out your old Yanni CD's and try it. The birds looked like swallows or sparrows, so we do not know if if works on gulls as we are inland.