"The federal duck stamp is the nation's most unique and successful conservation stamp. This program has been fueled largely by waterfowl hunters, who are required to buy a duck stamp each year and often buy more than one," said Greg Sheehan, service acting director. "Birders and other outdoors enthusiasts, artists and stamp collectors also buy duck stamps, recognizing their benefit to species and habitat conservation beyond waterfowl, as well as their artistic value."