Gi-normous birds (like the Great Horned Owls around here, and some Golden Eagles we've seen) are exactly why we started getting our girl in before dusk -- owls are mainly nocturnal, but can come out and hunt when it's still evening. Don't know the habits of Golden Eagles, but I do know they're huge, and also protected, so they can't be shot for killing one's kitteh.
Andria