Most turkey hunters carry a crow call with them, but many days it never gets used. However, sometimes, especially in the morning, gobblers will sound off at crows or crow calls.
Some hunters call these shock gobbles, the idea being that the loud noise of a crow flying overhead, or you and I blowing hard on a crow call, will elicit a gobble out of a tom even when he had no intention of gobbling. That is why a crow call is listed under the category of locator call. When you blow on a crow call, you are not trying to bring that gobbler to you, you just would like to know where he is.
A crow call is most effective in the early morning. Let's say you slip in within a few hundred yards of a gobbling tom, but then the bird shuts up. Did he get with hens or fly down with a couple of his buddies? Did he go to water, or is he having breakfast? What's happening out there? So jump on that crow call. Don't be shy - you are trying to be loud and obnoxious. Some of us are good at it right out of the gate, but for others it takes a little practice.
Whatever it takes to get him to open his beak. Now you have a chance of reading his mood. If it sounds like he is headed in your direction, find a good spot, sit down, shut-up and wait. If after a few minutes you can't stand it anymore, don't reach for a turkey call, reach instead for your crow call. The crow call is non-threatening. So far, I've never run off a bird using a crow call. I can't say the same for turkey calls.
A couple of years ago, hunting the coulee country of southeast Minnesota, I got a bird to gobble at my crow call. It was 8 a.m. and the woods had been quiet for an hour already. I killed that bird shortly after noon that day. He must have gobbled 50 or more times at my crow call. Sure that's unusual, but it shows what can happen - IF you have a crow call and are not afraid to use it.