Well if the ravens become a nuisance and are eating all the food that's for the backyard birdies, maybe you are justified in shooting one? I bet the other one will never come back, hehehe.
I shot one about 2yrs ago but I had no idea it was a raven. I mean my friend did..

There was a pair of what looked like crows that were way up high in a tree about 40yds out. It was September so the trees still had all the leaves on them, plus crow season had started. He found a small opening through all the branches and leaves where he could see part of the bird's body and took the shot with a .22 Condor. Next thing he knew this huge birds fell 60ft DOA that had a wing span of 3ft or more! It was a completely honest case of mistaken identity.
I have since learned that if you see 1 pair of what look like large crows, with no others around, it's a good indication that they are ravens, not crows. Ravens mate for life and don't hang out in numbers like crows do.
Here 's a pic of the raven he sent me

The Condor is 46" long so this is a good comparison of how big the bird and the wing span is (I measured 36"). A crow's avg. wingspan is 26" but can go up to 28-30" max. Raven's 32-36".