I agree with some of your knowledge on bird digestive systems but we are not talking about free range birds here. I agree that free range birds have a limited choice for feed but the birds in question are mostly captive birds. These birds while captive will resort to canibalism if they do not get the protein that they need. Pecking and eating feathers of other birds will be thier source of this protein.
I have seen this first hand and will encourage everyone to feed high protein feed to thier birds to discourage canibalism.
If AquaEyes has more knowledge with raising pheasants, I will take his advice.
I googled pheasant farms in Long Island, NY. I didn't find any results.
These thoughts are incorrect. First of all, protein is not the primary source of energy for birds -- carbohydrates and fats are. Secondly, you must understand that species evolve toward metabolic efficiency in their environment -- including the diet they are able to procure. Species which are able to acquire certain nutrients in high levels regularly will show a decrease in ability to synthesize those nutrients themselves because in so doing, they are economizing their metabolism. Individuals which are able to get by while expending or wasting less energy will be at an evolutionary advantage over those which are metabolically redundant. Thus species eating a lot of protein will not tend to have "protein-miser" metabolisms because it would not be an advantage maintained by natural selection.
Conversely, species living on diets lower in a particular nutrient will result in some individuals "getting by better" than others, and their genes will be passed onto more offspring. Being as chickens are a domesticated species, and until recently were usually living off the "scraps of the land", those most efficient at making a living on this kind of diet were the ones that had more descendents. Wild pheasant species have not undergone this evolution, and must be fed diets that closely match (in nutrient levels) those which their wild relatives consume. Similarly, from what I've come to learn from breeders, chickens' wild ancestor-species (red, ceylon, grey and green jungle fowl) will do very poorly on "chicken feed" and must be fed gamebird feed to do well.