although i have never used one,it would seem logical that a fawn decoy would work real well in the spring time when fawns are a part of a coyotes or other large predators diet.they would most likley work well through the summer months.as winter approches and the real fawns are much bigger they may not work as well.now the dead of winter when times are lean they just might work well again.now on the topic of moving decoys versus non moving decoys,moving decoys will attract(regardless of what it looks like)far more predators then non moving.i' ll bet you will find that a half dozen turkey feathers tide together,hanging from a tree limb blowing in the wind will ketch the keen eye of a coyote faster then a stationary fawn decoy.just somthing to think about.personaly i would go for the decoy heart before a fawn decoy.
www.decoyheart.com or go to bhw,s web site
http://lewand.tripod.com/barkmoon.html he has one very simalar at half the cost.