I had sheep once, - about 100 of them They DID actually get picked on by ravens during the lambing season, and so did mares while having their foals. Seagulls of the larger sizes also do the same, but the raven is way faster to the scene (much more clever)
This resulted in some really ugly casualties. If there was a slow birth, the birds would sit on the victim, start eating around the rectum/vagina, then the eyes and bowels. Very very nasty.
So, I started shooting ravens and gulls (back then it was not forbidden), and shot them by the dozens really. I found the nesting area of the Gulls (about 100 nests in a mossy field) and did not give mercy untill they had all packed and moved away:D
I belive that the Raven is not allowed to be shot anymore, however it is a possibility to get excluded from that rule in cases of emergency.
The raven, being smart does not really need to be shot by the dozens, shoot 1 dead, and let the dead one lay in the field, the others will stay away.
Alternatively, shoot them at 40 yards plus with a 12 gauge and a size 9 (clay pigeons), - they'll get the message and move without being seriously wounded.
I have some nice pictures of our local raven, and a tale to tell, - will post it later.