Quite a few things will set them off in the dark of night. I remember when I was younger and thought you had to be in the woods at least 3 hrs. before light hunting these birds...lol. Just the sound of a vehicle coming or going down a gravel road in the distance would fire them up at 3 a.m. Needless to say....I don't do that anymore...lol.
Different calls for different places, subspecies etc. Have always had pretty decent luck with a crow call first hour or two of light. Course like anything else there are crow calls and then there are crow calls. I use a Gibson Fat Boy most of the time...yes..custom...you get what you pay for in calls. Sporadic after mid morning. NE....woodpecker is my personnal favorite....mid day. Western Washington easterns...none work...roflmao . I have used owl calls on easterns only to get owls going....then later a response to the real owls...go figure.
Lots of other choices...coyote howlers, goose call in areas with geese...i.e. Lake Roosevelt etc., peacock...on and on...fog horn in a can....don't laugh it works...lol.
With any locator you have to believe and use it...they are not going to respond every time. But if you have a bird say 1/2 mile away, and you plan on moving on him....stop an use a locator like a crow call every 75-100 yards. You may only get a rersponse every other stop or every third stop. That's all you need though to keep an ear on him before you get close enough to set up and start hen calling.
