Preparing Poultry for Stock
With chickens, the whole weight will equate to about 52% boneless meat and about, 20% skin, and about 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 40lbs 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!