i have used CD,s in the past ,have a plastic eagle owl in the garden now.cant in all honesty say either have worked ? un-less of course attacks may have been worse without ? .there is a large feral colony only a few miles away from us ,and from whay i am told ,local fanciers get hit more often .we have around a 50/50 split at home of coloured birds and white only. will be interested to see what/if anything you come up with.