I agree with Micro Mike.
I normally have at least 3 different species in my set, of course it does depend on where I'm hunting. If I'm on the river generally only mallards or maybe a few woodies if I'm on a slough, but in the marsh I'm definitely mixing species. I've been known to use mallards, teal, pintails, gadwalls, widgeon and a few divers in 1 combo or another.
Now as for calling...hails in the distance...maybe,also I'll call on the corners as long as the other guys next to me are not callin and very very rarely a feed chuckle if they appear to be responsive and need extra coaxing, but I rarely feel the need.
When I'm out in the refuge and I'm watchin and callin to the ducks; the only calls that really carry any distance what-so-ever are the mallards. In my viewing experience I see all kinds of ducks come into range of other species wether they arre calling or not. In short, I think the idea of having to do a bunch of calling and learning all the other calls is needless.
Sure thing Hun, I'll get right on that...right after hunting season!