White Doves

I have enjoyed having a pair of White Doves nesting under the sola panels on my roof for quite sometime . It was lovely watching them 'kiss' and coo at each other.

Then this morning I discovered one of them dead in the garden. A local cat had killed it, I removed the body as the cat kept coming back for it. I am so upset as I understood they mated for life.

What will the other one do, does anyone know ? This morning it was sitting on the ridge tiles all alone.

This cat has previously killed a pigeon in my garden. Any suggestions on how to keep it out of my garden ?