Many hunters are familiar with the traditional "wheet-wheet" squeal that a woodie makes in flight, and most call manufactures produce these types of calls. Because they are fairly loud, these calls are effective in getting the attention of most wood ducks. Woodies have a much wider vocabulary though. Just listen closely to a roost one morning and you'll be surprised at the various sounds you'll hear. Most of these roost-type sounds can be achieved by choking down your call with your hand and modifying the way you blow into it.
When I'm hunting woodies I'll usually get their attention with that "wheet" sound and then switch over to a completely different call such as the "wood duck whine." I have oftentimes seen woodies produce this sound and, once they get a response, they will then swim over to the rest of the flock. The WW-90 is a very soft call that cannot be heard at a great distance and it simulates a locating sound that the ducks make, usually after they land.
This is definitely the call of choice when the birds are within 150 yards. Try and watch them key in on this sound! Also, using a few decoys will certainly help in having a visual. The key word is "few" since it doesn't take many to make a difference.
So, while you may not ever get woodies to respond as well as mallards to a call, the proper techniques of calling them can open up a whole new way of hunting woodies. Plus, you will find it much more enjoyable as well. The only problem you may encounter is proving to your buddies that a person can indeed call in a wood duck. Come to think of it, that may not be a problem at all since there is a little ham in all of us!