Larry, we had a lot of pheasants in the 90s and we had about the same amount of trapping (close to nothing) and probably even more predators, especially foxes. The loss of farmsteads and old barns and other outbuildings has dramatically reduced some predators like raccoons, skunks, and opossums. I don't know what the status of foxes are statewide, but around here they seem to be just coming back however slightly from a long hiatus.
Most people that study these things put a lot more emphasis on winter kill hens and especially spring nesting conditions.
Brent, coyotes tend to control fox populations. We had a lot of pheasants in the 90's due to CRP--especially all the "full field" variety, much of which we lost as a result of the 1996 Farm Bill. Overall CRP acreage, Iowa looks good comparatively speaking . . . but much of it is now in buffer strips as opposed to the big fields we had prior to the changes in the 96 Farm Bill. But stop to think how many MORE pheasants we would have had in the late 80's and 90's if trapping pressure had been what it was a couple decades earlier. Studies done by Delta Waterfowl have established that intensive trapping will increase waterfowl production on prairie potholes surrounded with decent habitat. Unfortunately, that doesn't work on the kind of "macro" scale that would be required to have a significant impact on upland bird numbers. But when we had that kind of trapping pressure simply because fur prices were higher and there were a lot more trappers, that helped to offset the fact that we didn't have all the really good habitat that existed in Iowa for about the first decade of CRP. With the push to larger farm fields, we've also lost a lot of the "micro" habitats--fencerows etc--that we used to have. Sort of a "death by a thousand cuts" situation. Farming in Iowa is far less diverse than it used to be--and it's hard to imagine that it's going to change much to benefit wildlife in the future. Barring programs from DC. And it doesn't appear likely that we're going to regain the 10 million acres or so of CRP that have been lost since peak enrollment.
Iowa's grouse decline was mostly a habitat issue. Not much logging going on, and essentially no clear cutting. Same thing happened in SE Minnesota and SW Wisconsin. All those areas offered--at least through the 80's--very good grouse hunting. But the increase in nest predators was almost certainly a secondary factor where grouse were concerned as well.
Back in 1987, when I was assigned to an Army Reserve unit at Ft McCoy, we had a female officer who was married to an active duty officer stationed there. He killed 20-some grouse hunting on post without a dog. That won't happen these days, sad to say.
When the Iowa DNR finally got around to doing an inventory of the forests on public land, they found that the amount of early successional habitat was very small. They've tried to do edge management since then and have worked with private property owners surrounding public land on habitat improvement as well. But it's largely a case of too little and too late.
