Migratory bird hunting stamp:

In 1934 in an attempt to bolster the Migratory bird treaty, the U.S. Department of the interior, instituted the Migratory bird hunting stamp.  The purpose of this stamp was to help pay for the study and protection of wetland habitat in both the United States and Canada. Stamps such as the one below were required by all hunters who hunted waterfowl.

Individual states also enacted a stamp and fee to hunt waterfowl on state lands.  Both the federal and state programs have helped stem the destruction of wildfowl habitat on the North American Continent.