This is a good question Fullback!I' ve seen it many times and I do believe it has to do with the genetic make-up of the bird!Age,food supply,area,and specie all play into this somewhat but some of the physical characteristics can be detected by the passing down of there own genes!For instance,a couple of flocks of birds I hunt the gobblers just dont grow decent spurs!Its common to kill an adult gobbler with no spurs or only 1 out of these particular flocks!In another instance another flock of birds are known for having 3 or 4 bearded hens in it every year for about the last 15 years that I know of!And finally one other flock I know of continues to produce gobblers that have multiple beards!It isn' t like these flocks are new to me,i' ve been hunting them for years and its no question in my mind that each generation keeps passing those particular traits down to there offspring!!!Bob