M.P.
UGH I HATE crow/ravens. horribly smart birds. I think the owl thing will work for a day or two till they figure out that it won't attack. I would call animal control and ask what you can do.
Lol So I'll tell you my run in with ravens. I was camping in Southern Utah and we left our campsite to go on an all day hike, Everything was in giant plastic boxes with LOCKING lids. When we came back EVERYTHING but the marshmallows were all over our campsite with the ravens flying over head and some still picking at the bread. Yeah, not a fan of the stupid birds. Thank goodness it was our last full day other wise we would have had to leave early to get more food.