All the corvids - ravens, rooks, crows, magpies, jackdaws, jays - will grab anything they can. Ravens are the worst, picking out anus, tongue, navel and eyes in a few minutes whilst the ewe is under the hedge producing the second of twins. Crows go for the eyes of any ewe that's cast. Used to be the gamekeepers shot them whenever they saw one but it doesn't happen now. Magpies and jackdaws are major predators of wild birds eggs in tree or hedge nests.