The state could spend 10 Billion dollars and not be able to return to the glory days unless they address farming practices.
Morris, I'm assuming your talking strictly about S. IL? You're correct. We don't know why birds have never taken to S. IL.
As for the rest of the state, farming practices are one of the obvious issue we're facing.
But I will say, throw $10 billion into the rest of the state and I'll show you pheasant #'s in Illinois that would blow your mind.
I realize your exaggerating the amount to make a point, but the fact is, a well funded and focused IDNR can make a huge impact on wild pheasant populations in Illinois.
For example, at one time my IDNR habitat rep and the IDNR would aid/instal/improve/etc habitats that were as small as a few acres on private lands.
Now (due to a lack in funding and man power) he won't touch anything smaller than 40 acres. Time and $ is no longer there for smaller, less significant habitat areas. The result is further decline in habitat because as we know, pheasants need to move, and need smaller habitats too.
Illinois lost it's increasing pheasant population in the winter of 1995. Why our birds have never returned to their previous #'s is a mystery. This is the big question; Why not
Farming practices, predators, gene pool, disease, etc? Yes of course. All are factors. But why such a sharp decline without a return?
Did farming practices change that much in one year? I don't believe they change enough to drop our bird harvests by the hundreds of thousands.
Declining CRP? We lost some 1996, yes. But enough to keep our wild pheasant #'s from even coming close to returning to 1995 and pre 1995 levels? Not likely.
Increasing predation? Sure, coyotes were on the rise from the 1980's through the 1990's. The problem is, pheasant and Hun populations were too. Right alone with increasing predator #'s. So this too is not likely the culprit.
Here's a few things I've noticed with birds here in N. Il. pre and post 1995. (My own observations. This is obviously non-scientific) though we are finding that our birds are genetically similar throughout that state through a wild pheasant DNA testing program here in Il.)
1. pre 1995/96 our birds had orange colored eyes. They are now yellow on most birds I observe.
2. pre 1995/96 our birds had no problem crossing roads anytime of the day. Now, we seldom see wild birds along the roads (even in areas with healthy bird #'s), and rarely see them crossing roads either by flight or on foot. Most birds I've witnessed crossing the roads in the late evening when it's nearly dark outside.
3. Roosters used to be seen with many hens in his harem. He'd breed with a hen then move onto the next hen. Now some of our roosters are seen with one hen and staying with the hen to help raise the chicks. He's not breeding more than one hen, despite a number of hens in his area. Could it be, many of our wild roosters are not breeding as many hens as they could be? Could the survivors of the winter of 1995 be of a unique gene pool? One that has characteristics different from the general populations of 1995 and sooner? Could this survivor be behind our declines? Not because he's not worthy, but has habitats that hold our pheasant populations down from what they where and used to be?
Okay, this post is getting very long and i apologize about that. I'll finish my rant with this; We all know we need habitat. Where we have proper habitat we have wild birds (s. Il excluded). I'm seeing more birds this year than I have in many years in areas with the habitat needed for a healthy wild pheasant population. To be honest, there should be more birds in some of these areas considering how prime some of these areas are for producing birds. Hopefully this year's increase will be a growing trend in areas with the proper habitat.

Time will tell