Wabana, if you need to shoot non - toxic ammo and you do not want to open up the choke for steel shot, there is an answer. It is called Kent Tungsten Matrix ammunition and it is tungsten dust suspended in a polymer ball. This gives the same density and malleability as lead, so shooting it out of a full choke is OK. In addition, it has the same (maybe a little better) killing effect as lead shot. You can become very unpopular as you pick off the ducks just outside of the range of the steel shot users. It is truly wonderful ammunition, available in 2 3/4, 3 and 3 1/2 inch loads.
The drawback is that it is really expensive - think $4 per shot. This is OK if you are just hunting waterfowl occasionally, but could be prohibitive if you shoot ducks and geese all season long.
If you hand load then there is NiceShot available, similar density and softness as lead and an approved non - toxic shot. No factory ammo loaded with it in Canada, though.
Sharptail