This is when to use your gear to improvise killing-zone boundaries.

Set the outer edge of your decoy spread at exactly 40 yards -- or at the distance of your effective range. Hunters who use "wind ducks" or other devices can use them to create a set of known distances.

Pass-shooting over big water presents the most difficult range challenge in waterfowling.

There are no decoys, nor any objects to establish known distances. And the horizon is often obscured or disappears into the water.

On dry land or in areas shallow enough to wade, you can plant a few unobtrusive stakes at appropriate distances. In deeper water or tidal areas, a small float will do the trick -- if you have a way to put it out and later retrieve it.

You can also use "confidence decoys" like herons and swans to give a sense of distance and perspective.

QUICK! WIDGEON OR TEAL?
Here are three steps that will help you automatically identify ducks and geese species at a distance.

1) Begin with life-size duck or goose decoys. Set them out at different measured distances. Memorize features on them that you can identify. Try to do this in the same type of places you will hunt, at the same time of day and during similar weather.

2) Study ducks and geese. Fortunately, waterfowl are abundant in city parks and golf course ponds, along public beaches, at state wildlife areas and national wildlife refuges. The most common species are mallards and Canada geese. When they aren't being hunted, their relative indifference to human activity gives you a great opportunity to study them.

Observe how they appear when you are out of range. Then move closer. Identify the features -- wing patches, colors and other markings -- that you can see regularly when the birds are at various distances within your effective shooting range.

3) To make it more authentic, go to the marsh, field or lake early in the morning or late in the day. When ducks and geese begin arriving from or leaving their resting area, you can see the birds in flight -- and they will look quite a bit different from stationary birds on dry land.

In time, you will start to notice those little details (the white ring around the neck, the color of the feet, the apron of white on a mallard's tail) that can tell you when the bird is in range. Try to observe flying birds in low light and during bad weather.

I'm realistic enough to know that not everyone will actually begin to train himself to judge distance by watching ducks in the off-season.

But those who are fascinated by the animals they pursue -- who learn about them, who observe them in the wild and respect them -- always become the most successful hunters.