Posted: 02/09/2012 at 10:34
Yikes spikes
If you have cats in the neighbourhood its very hard to stop them doing what unfortunaltly comes natural to them.
I have had to strike a balance also. I feed black birds and have many kitties trying to get them. I use a water squirter and chase them out to the front garden where i give a reward them in the way of treaties and this trains them to wait out the front and not enter the back.
I use to have a cat that chased all the others out of the garden and sat next to the black bird whilst he munched his way through his breakfast. Unfortuanatly he passed away and now the jobs mine. So if you want to scare the kitties out your garden - get a tom cat and he will see them all off. 
Failing that stop feeding the birds if looks like its going to mean the demise of them.