Great conversation here and very civil - unlike most of these discussions on Internet forums.
I was a wildlife manager in Michigan. I did my college work on ruffed grouse, and worked on deer, turkeys, grouse, the Sichuan pheasant program, waterfowl...habitat management, etc. I managed a state wildlife area in southern Michigan and worked in the U.P. My family and in-laws live in the Traverse City area. I have extensively hunted throughout the state of Michigan (deer, Turkey, rabbit, squirrel, waterfowl, pheasants, ruffed grouse )and have also extensively hunted Wisconsin (deer, grouse, pheasants, waterfowl) North Dakota (pheasants, waterfowl, sandhill cranes, sharp tailed grouse)Nebraska (pheasants, prairie chicken), Kansas (pheasants) and Colorado( deer, elk, pronghorn, pheasants, doves, waterfowl). I say this not to brag but to just point out my hunting experience juxtaposed with my biological knowledge and experience as a wildlife manager.
It is indeed a fact that all wildlife species have their own set of unique habitat requirements for breeding, birthing, bringing up young, and survival to breeding age. But "habitat" is THE basic requirement. Considering habitat Ina most-general sense, there can be "habitat" devoid of good numbers of critters, and there can be limited numbers of critters existing in very marginal "habitat". This is especially the case in areas which are marginal range for the species under consideration.
The lower the quality of the habitat for a given species, the greater the impact on that species from other negative influences. Take pheasant predation for instance; in the Dakotas, with its seas of grasses and agriculture as previously described, there are tremendous numbers of predators. But they have very little overall impact on pheasant numbers because of the sheer abundance of high-quality, year-round "habitat". Pheasants, being non-migratory gallinaceous birds (as are ruffed grouse), need all their life requirements in a relatively small area. It is generally agreed that where ALL life requisites for the ring-necked pheasant exist in about a square mile, there is a good chance pheasants can be sustained, and where they do not exist pheasants will not and cannot be sustained in any significant numbers over the long-term.
Islands of seemingly ideal pheasant habitat, which exist throughout many parts of the Midwest, might be able to support a few birds now and then. However, as the landscape in southern Michigan, southern Wisconsin, Illinois, Ohio, southeast Minnesota, etc., has transitioned from a family-owned "farmscape" with lots of "waste" and "inefficiencies" to a corporate-owned "agriscape" with just the opposite, the only thing that exists in many places are relatively small islands of habitat which are incapable of supporting sustainable populations of pheasants over the long-term. The "pheasant states", as many of you know, have tremendous amounts of large blocks of habitat. Here in Colorado and western Kansas pheasant numbers wax and wain due to the impacts of seasonal weather...we can have a great hatch in the spring and lose almost all of the production in localized areas due to hail storms (which we get a LOT of!) or drought. The last three years we have had very few birds on tremendous amounts of acreage suitable for pheasants...but they will come back to relative abundance given advantageous weather conditions. And I will be out there hunting them until the season ends of January 31st.
This is a large part of the basic argument against "stocking" pheasants. The average life span of the ring-necked pheasant is 9-11 months, whether they are hunted or not. This DOES NOT mean that some birds don't live to 2 or even, in some cases, 3 years - they do. But AVERAGE, in the WILD, is 9-11 months. So the sustainability of a population relies upon "recruitment", which depends upon "fecundity" and ... "Habitat". So large areas of marginal habitat which might seem ideal to some are simply incapable of supporting a significant number of birds over time. Lots of corn is not year-round habitat; lots of smooth brome grass is not year-round habitat; fields of indiangrass and switchgrass surrounded by tree rows and wood lots (all predator perches) in not year-round habitat.
So when it comes to hunting, in December or otherwise, for r-selected wildlife species it is still a compensatory mortality factor. Hunting CAN BE an additive mortality factor when the islands are too small - if you have a rooster and three hens on your '40' in the Thumb and you shoot the rooster things don't look good for your "pheasant population". But the reality is that rooster's (and the hen's) odds of surviving to breeding season are not that great. The idea with pheasants is to survive to your first breeding season. If that happens generation after generation, you can have a sustainable population; if it doesn't, you can't.
And we just aren't that good at "hunting" for the most part. We can't smell, we can't see, were noisy and unstealthy, and we are only out the practicing it for a small percentage of the year!