It might work okay, but you might want to consider the DKW-1 LT model instead. It goes to 20KHz on the high-pitched side of things, for only a few bucks more (very few bucks more, these can often be found for ~$45-50). Though I've not used one myself, a number of fellows here have, with good success. The receiver of the DKW-1 will more compact than what I see pictured for the 121, although it too requires an external 12V battery of some sort, and also requires an external amp. But if you were going that route anyway (crow calling requires a lot of volume, no?) I'd think it'd be more versatile and a better bet.
LionHo