We too have had problems with cats killing birds and ruining our flower beds & seedlings,the first problem we simply took the bird feeder down as the birds didn't stand a chance with the high concentration of cats we seem to have round here,(a lot without bells on!!).The second problem we solved to complete satisfaction, this involved turning our patch into a gravel garden & deterring any cats who were still intent on using my garden as their local toilet with a spray on the old garden hose.With these two methods i can give a 98% guarantee that you will never have a cat use your garden again as a toilet,the problem with cats hunting wildlife however cannot be solved,the only way to limit it is to put bells on them to give the wildlife a head start.