Just been out to replenish the bird feeders and found a wee pile of feathers. Hope it's not my tame blackie - and Millie the neighbour's cat had better stay away. Water pistol at the ready.
I have twice seen a sparrowhawk kill and eat a bird in our garden. On one occasion there was just a 'wee pile of feathers' left behind. Every part of a blackbird was eaten then, but a pigeon proved too large a meal: only the head, neck, breast were eaten. Most of the body was left behind, plus plenty of feathers, but it did look rather tough meat, so I wasn't surprised!
Oh dear yes. We had a little pile of feathers in the garden, was upset one of the cats was to blame and then a few weeks later looked out of the window and saw a sparrowhawk in the border plucking what turned out to be a long tailed tit. Horrible but that's nature. Didn't expect that in the middle of a housing estate.
Predators will be predators.
The best thing to do, is make it harder to hunt their prey by providing some form of refuge that the smaller birds can escape into, nearby, like some dense shrubbery, ideally something thorny like holly, that may deter lurking cats.