I'll clear up what my point is:
I'm talking what is needed in the OVERWHELMING landscape theme of a particular upland bird.
For example:
Pheasants CAN NOT exist in the dense forests of the UP of Michigan, despite the occasional "grassy meadow" interspersed in.
Chukars will NEVER make it in the grassy/cropland of South Dakota. Nor would they EVER survive in the UP of Michigan.
Ruffed Grouse WILL NEVER make it on the prairie of Nebraska despite a few trees.
Some birds can, however, overlap a bit:
Pheasants and sharptails: 10-25% overlap
Pheasants and huns: 5-15% overlap
In Idaho, I have flushed chukar from a rocky cliff, then walked 300 yards from that to a grassy plateau and flushed huns, then, within a mile or so, flushed a rooster from a creek bottom. That's the "overlap" I'm referring to. For sure, each flushing from their little niche, but I'm still on the same walk.
I have NEVER flushed a sharptail from waist/chest high CRP. But, walking from this CRP 200 yards down a 2-track, cross a fence and into a cut sunflower field, I'll flush sharpies. The extreme of overlap is one experience we had flushing huns, sharpies, and roosters from thickets in a mile long draw in ND.
Minnesota does have some "overlap" with ruffed grouse and sharptails but it is extremely compartmentalized. Ruffed grouse in the woods, sharpies in the relatively open meadow-type fields.
Huns flourish in the vast wheat growing areas of Saskatchewan. Almost NO CRP-type grass but some prairie grass. As a result, this is how the numbers stack up:
Huns: 80%
Sharptails: 19%
Pheasants: <1%
The northern part of the Nebraska panhandle has one the best "overlap" ratios I've seen. I guess about a 50-50 mix of pheasants and sharptails.