Guys,
Here's my 2 cents worth:
This year, pheasant numbers are down from last year because of: (1) a very hard winter (record snowfall during December, near record snowfall over the entire winter, and colder than average temperatures) and (2) an unusually wet spring that flooded nests and caused more chicks than usual to die from exposure. In other words, most YEAR-TO-YEAR fluctuations are caused by changes in WEATHER.
On a STATE-WIDE basis, pheasant numbers are down over the LONG HAUL because of a LOSS OF HABITAT - period. An incredible number of things have changed during the last several decades in Iowa. The farming industry has completely changed to the point that most small, highly diversified (multiple crop types, brushy fencerows, grassy areas, farm lot groves) farms have been combined into fewer, larger, "cleaner" farms that are growing only 2 crop types (corn and soybeans).
Obviously, the advent of the Conservation Reserve Program added millions of acres of at least marginal habitat to Iowa's landscape during the 1980's and 1990's, allowing pheasant numbers to return to much higher levels in many parts of the state.
Now, we are losing pheasant habitat back to agriculture because less and less acreage is enrolled in CRP. As a result, pheasant numbers are declining.
On an INDIVIDUAL PROPERTY BASIS, any number of things can cause a pheasant decline. Most often iit is weather and loss of habitat, although increased predator densities can also have an effect at a local scale.
OrionWhitetails