In reading Keith's post on Pennsylvania pheasants there are other factors that helped in the decline and most of it was due to the people that run the agency.
Back when Pennsylvania was in the top 10 in pheasant harvest, close to 1.3 million in 1971, and exceeded South Dakota for a year or so. The reason was that the state released chicks at 5-6 weeks of age on land that was not posted. By the time the season came, these birds were almost like wild pheasants. There were times pre-season working the dogs that you would put up 50 or more birds around the Coply- Ironton area outside of Allentown. This lasted until the state stopped the young bird release.
I have read now that the total release is way below the 200,000 and is under 100,000.
The state did start a new program on using either Kansas or South Dakota wild birds and releasing them on special areas with no hunting for a few years. The trouble is these areas are not conducive to pheasants.
It's the same with the Trout fishing, gone bad and is getting worse. I don't hunt deer but have friends that say the deer population is declining also compared to 10 years ago when spot lighting at night and seeing deer in most of the fields.