SD Pheasant Hunter Numbers on the Decline

From the story on KTIV.com:

The number of pheasant hunters in South Dakota last fall dipped for a third straight year. The Game, Fish and Parks Department estimates there were 69,959 South Dakota hunters and 97,350 from outside the state. It's the eighth straight year there were more nonresident hunters than resident hunters. The GF&P says hunters killed just over 1.6 million pheasants. Spink County had the largest pheasant harvest at 93,770 birds, followed by Lyman, Brown, Tripp and Beadle counties.

Poor economy? Dwindling birds? Less land access? Or just a continued decline in the popularity of upland bird hunting?