In many ways, it’s a common marketing situation: a manufacturer faces dwindling sales of a venerable product due to a shrinking core market; an ancillary market holds some promise but its growth potential is hindered by pricing issues.

In other ways, it’s almost unique: most of the people who buy the product do so because they have to, not because they want to; and most of them have no idea what the product is used for.

Then there’s the product itself: duck stamps.

Duck stamps? Well-known to duck hunters and stamp collectors, the U.S. Fish and Wildlife Service’s Federal Duck Stamp Program has, since 1934, helped fund the preservation of over five million acres of wetlands in the U.S. Unlike many government programs, this one is a model of efficiency: well over 90 percent of its revenues go directly to the purchase and preservation of wetlands. The rest is used for production and distribution of the stamps.

Known in official parlance as Migratory Bird Hunting and Conservation Stamps, duck stamps are a required annual purchase for duck hunters. (Most hunters say they have little idea of what duck stamp fees are used for. They just know that you have to buy a stamp if you want to hunt ducks.) But the number of hunters is decreasing, and though the stamps are sought after by collectors, their hefty price (last year’s stamp was $15) makes accumulating them an expensive proposition for the garden-variety philatelist.

“We needed to find a way to reach a new audience, to broaden our market, as with any product,” says Margaret Wendy, manager of sales and marketing, Federal Duck Stamp Office, Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C.

So the government has embarked on a test print and TV ad campaign appealing to conservation-minded individuals by offering them a chance to preserve wetlands simply by purchasing a duck stamp. For $30, they receive a...