I bought some of the plastic crow dekes and I even found some around Halloween even with feathers on and they were cheap!!!!! I as well use a Johnny Stewart caller and as other have said hide in the edge of the timber.
We have even used a piece of grey 10' PVC pipe with an owl decoy on top on the edge of the timber for them to look at when they get there and the crow dekes on the ground to add eye appeal. I took one and wired it to the pole just under the owls feet to look like it was in his grasp and did it really drive them nuts.

We tried last year in the middle of a picked corn field with our waterfowl lay-out blinds and it was really nuts for the crows came within yards of us!!!! We placed the owl deke on a fence post and the lay-out blinds in the grass near it.