Yep they work especially well, the more wind the better. Even had Canada geese come in to them during a snow storm. Used them in a long line with the metal shower current hooks to hook them to the main line. Cheap and effective. You can add some water to them to get them down in the water when there is little or no wind. We used them on a point when we had to walk in. If we knew we would be back the next day just hauled them up on the shore and left them there. No big deal if someone took them.
We even used round balloons (white) and stuck a branch in the water and tied about 3 foot of line to it and than the balloon. The wind would blow the balloon making it look like ducks tring to jump the flock to get to the front. Works pretty good, only thing you'll have to replace the balloon every now and than because they would shrink in cold temps. The balloons worked really well when you had a nice easy breese with small burst of harder wind. The balloons would lift up and than flutter down, simulating birds rising and landing again. Used them in conjunction with the jugs.
Leave the bottom white and a patch through the middle white and the rest black. We used the small bricks that had holes in them and could run 15 jugs to a brick.