Preparing Poultry for Stock
With processed chickens, the whole weight will equate to about 52% boneless meat, 20% skin and 28% bones.
Game birds will be different but not dramatically so - except that they will have much less fat.
So, for instance, to get 12 lbs of bones you may need over 40 lbs of poultry.
Regardless, save the skins! Tremendous flavor there - even from store-bought critters. Of course with game that means you need to do a thorough plucking job... which can be a big hassle!
Normally your limiting factor for the number of "Servings" is one of two things: the weight of bones you have available, and the size of your largest stock pot (unless you split it into multiple pots).
So fiddle with the pot size below until you come up with a number that is both a) not bigger than your biggest pot and b) not more bones than you have on hand. All of the other ingredients will fall into line.