Iowa has lost so much cover, CRP and fencerows,etc, that there is practically no place for a pheasant to safely nest and rear her young or to hide and escape predators and old man winter. Back in 1980s I used to pheasant hunt Iowa every year and did very well. I believe that Iowa has lost more CRP acreage than any other state.
In addition to the loss of so much of the CRP the fields became much larger, fence rows were removed and a total monoculture installed so that larger equipment could be used to make more money. The ethanol craziness has only turbo charged these changes, with CRP rates being so low is simply is not economical for a farmer to put land into CRP.
Then Mr Rooster just faded away.....
Someone mentioned the land management practices above and the resultant diminishing of the bird food supply. Birds eat bugs, too. In Iowa, which used to be a wonderful pheasant state, I believe the herbicides/insecticides have spoiled that pheasant population. A year or so I talked to a farmer of many decades and he said he had not seen a grasshopper in 3 years.
