This year I think I have lost more to Ravens but I know that foxes and badgers can take lambs too (I have seen all 3 do it)
The ravens seem to land 10 m from a ewe and lure one of the lambs off with a little dance, lamb becomes interested , follows for a few metres and then the raven delivers a mighty wallop to the lambs head
yesterday I saw this happen (through binoculars ) to a lamb born 24/4/14 ---that's almost 4 weeks old!
The thing I find sickening is that the raven just seems to want to kill the lamb and maybe peck out its eye--at least the fox usually has a meal out of a lamb