I usually throw out two to four teal blocks per 24 mallards, and lately have been throwing out bluebill blocks as well. This was working very well until our ducks dissappeared a couple of days ago... (they' ll come back- they always do!).

Not only do I mix in other species, but I try to make a point of buying a dozen of a different style of mallard blocks every year or so. This way I get different head positions and texture/color. My new favorites are the Herter' s Millenium deeks. They are a bit on the spendy side, but seem to be like magnets.

This stuff works for me, but you never know.