I have a bird feeder and a heated bird bath. My cats love watching
from the window, and when I let them out (fenced in yard) I make sure
to loudly announce that they are coming. Still, birds aren't terribly
smart and three have been caught over the last few years. I was able
to rescue two before they were dispatched.

It's pretty funny to watch the cats hiding under the evergreens, not
even six feet from where the birds are on the ground below the bird
feeder. Mostly the cats just watch though. They're pretty well fed. As
are the birds.

It's funnier when they try hiding under the rhododendron in the
winter. Bare branches don't really hide them all that well, but it
seems to be enough to fool the birds.

Still, the bird feeder is on a pole which the cats can't climb. I
don't think I'd just put one in a tree where the cats could get at
them more directly. Let's not make it too easy.