trya one of these, my cat hasn't had any birds since i put one on his collar BLING BLING BLINKER FLASHER LIGHT.... BLUE.... FREE P&P on eBay, also Collars Tags, Dogs, Pet Supplies, Home Garden (end time 29-Jun-08 18:04:11 BST)
i got mine from the pound shop ..... for a pound
though it might not be much use if the birds can't fly anyway all you can do is keep the cats inside for a few days when you notice the birds fledging