Many birds of prey, e.g. Accipiters, prefer doing it on the ground, as said above mammals in general, not only cats, don’t pluck out feathers, so you can see fairly easy when it’s a mammal kill, e.g. this killed by goshawk probably, this one by sparrowhawk, and this one by cat.
@ram_k cause they kill not because of starving, brains are more nutritient and tasty than other bodyparts, also liver too, but head is easier to eat.