"Grounding Your Flying Ducks..."
Both Bantam and Wild breed ducks, as well as some Light class ducks, are VERY capable of flight! You can "ground" these birds to keep them from flying around or flying away. Below if a chart showing you a few options on what and how much to trim. You will only need to trim one wing to keep your birds on the ground.  (Please read the sidenote at the bottom as well.)
This diagram shows three seperate ways of grounding your ducks.
Figure A shows: Full wing (new flights growing back in.)

Figure 2 is a partially trimmed wing that leave the outer two primary feathers so that when the wing is folded it gives you the two criss-crossing points over the back.

Figure 3 shows all 10 flight featherrs completely cut off, just under the Primary covert feathers.

(*When trimming flight feathers, be careful not to cut into the quick, as it will cause bleeding. A good guide to follow is 1 inch below the wing coverts.)
When you trim the wings of your ducks you have stopped them from being able to fly, until the molt and grow new flights. By taking this ability away from them you make it so that they can not fly should they be required to take flight to flee predators. Strong fences and vigilant protection are a must with clipped or pinioned birds. On the other hand, if you have expensive birds that are capable of flight without a well covered and well fenced pen you are asking for trouble! So in order to keep these birds inside fences, they should be clipped. If you are simply turning birds loose to swim and free range on a pond, and don't want to lock them up every night in a safe shelter, then they should remain full winged.
Some of our Mallards are clipped and others pinioned, but as a rule we do not clip wings. We do not feel that we need to do so, and most of our birds have been here long enough, that even if they do fly, they come back almost instantly to be let back into their pens.