Scarecrow is probably the worst idea there is, As in my beliefs you want as many crows around you as you can get a scarecrow would detour them elsewhere. Try introducing bird baths and feeders in different spots through out your yard try to call as many birds in as you can. That is what I do. Keep in mind birds can carry disease. But the smaller birds detour hawks away from your/there propertys, Mockingbirds sparrows swallows crows ect. I have actually seen crows gang up on hawks and really do some serious tormenting to them. CD's work a few times best to never leave them in one spot to long constantly move them around. plastic hawks can somewhat work as well Mounted on trees or fence posts. Also decoy crows How ever anything that doesnt get rotated around will just become normal to a bird of prey. Owl decoys arent bad. these are a few of the legal solutions that dont really seem to work 100% of the time.
There are a few more solutions that I will just keep silent for now hope this helped some.