Cat Owners....Help me!

I have sat here awhile wondering if I should really post this. I don't want cat owners disliking me. Well, I am trusting the caring blip community to be tolerant of me and my rant.

Please help me ! I am wondering what to do about a couple of neighborhood cats who come into my yard. This one was sitting on my deck railing near my bird feeder and caught one of my favorite little birds; yes, he killed it; that was yesterday, today he came back and I chased him off and then saw him sitting in my garden so I took this photo.  I often find bird feathers and remains in my yard. I do everything I can to attract the birds that we enjoy watching, so this makes me sad. 

Also, this one and another orange/white one are digging in the sand of my newly laid pathway and going pee and poop in there. Yes, I have seen them and the evidence is still out there.   This summer I removed a plant to give to someone and I was told they didn't want it because it smelled like cat poop/pee; I went back to the area and saw that there were many piles of poop barely buried in the ground. Yes, I add sand to my clay soil; but I didn't intend it to be a litter box for my neighbors cats. 

Here is my question? Should I have an expectation of cat owners keeping their cats home? Do I approach them or do I simply clean up the messes and not worry about the birds they kill? Do I remain quiet. How do I handle this sadness in my life.  I like the cats, they are pretty and healthy well fed and well loved cats.....but I don't like what they do in my yard.

Thanks for any suggestions.