Blacks are far more wary than mallards are....one of the most difficult birds to decoy, if not the most. I'll give you my opinions one at a time.

Black duck call: The hens sound just like mallards do. The drakes sound just like drake mallards do as well. In order to make that grunt sound you hear, you need either a 6-in-1 whistle, like the teal/widgeon/sprig/quail/woody etc etc whistle, or a Duck Commander Mallard Drake call. With that whistle, just grunt like you normally would into you single reed and say "drake", short or long, loud or quiet. Just sort of buzz your teeth a little. I have also heard people say "zzzzztttt", and that works well...drake just makes more sense to me.

Decoys: Blacks will land with mallards, most anything will. But, they prefer to hang with other blacks. What I do, is mix my spread with mallards and blacks. I will usually put the blacks a bit off to one side, and mix one or two blacks in with my standard 8 mallards. Occasionally, I will throw in a sprig or a widgeon just to add some white. If I am near open water, I'll use a bluebill or two. The key is location. Its been my experience that black ducks will only decoy in certain areas...typically, tidal creeks in marsh, but preferably along a tree line. Some of these creeks can be pretty dad gum small (not much wider than your john boat), but thats where they like to be. I have had a devil of a time trying to get them to land along the side of a river, even though mallards will land there all day long.

Species: Everything will land with mallards, it is true. But, if you want to kill widgeon, then you are going need a few baldplate deeks. I have killed some over mallards, but noticed that I started seeing a heck of a lot more when I threw out a few off to the side. Wood ducks are no different (only they don't reliably decoy to anything, even just wood duck decoys....they do the flyby). Pintails are right up there with blacks as some of the hardest to decoy. Most of the sprigs I have killed have been extracted from groups of mallards. For the most part, if you want a group of sprigs to come in...you need a spread with predominently pintails. There again...just been my experience.

Calling in general: I hear a heck of a lot of commotion in the marsh from other hunters...and it isn't gunfire. My general attitude with calling is that more is less. If the birds want to come in, let the decoys do it. Calling for me serves one of two purposes....one) an attention getter....ie, the ducks don't see the decoys, so the call makes them curious...works very well on low birds. Two) a deal sealer...when the birds have worked once or twice, a few quacks or a greeting call when the swing around down-wind will usually hook them right in. I don't call to every bird that comes by...because thats not what ducks do. I don't live in Arkansas....where you don't even need decoys to kill birds in the flooded timber (lots of chatter and lots of water movement will do it). This is just what I do...and I have acctually killed more blacks this year than mallards (of course, the ducks are all still up north for the most part...but the front is coming down tmw AM! I'll be there!