I've tried a lot of mechanical decoys and I was really upset about that, because it was really complicated. But afterwards I've tried some awesome application for my iPhone. This is called “Decoy: Ducks & Geese”.
Hunting ducks never was so easy. You will not be disappointed, because these sounds are very similar to real decoy. But this yelper is much better and easier to use!
You can watch some fun video about this decoy http://www.youtube.com/watch?v=tMz1OPhQK_s
and you can also download it here http://itunes.apple.com/us/app/decoy...367285907?mt=8. You will be totally satisfied with this decoy.
Decoy: Ducks & Geese - an application for iPhone
