I think the Mailman has the answer for this under the thread Good or bad year.I will copy and paste it for you here:


Respected biologist and turkey hunter, Lovett Williams, seems to think that turkeys can self regulate their populations. He feels that turkeys can determine carrying capacity for theland they are on and choose to nest or not based on the circumstances.
This has been studied in areas where the turkey has been relocated in order to build sustainable hunting populations. In many of these areas there have been large population gains in the first few years followed by reduced hatches once the populations have reached higher levels.
Another sign of this may be when hunters spot gobblers with hens late in the hunting season and claim that the gobblers are still all henned up and hard to call away, even late in the season. Perhaps someof those hens that the gobbler is courting are actually in an off year and may not breed at all...

I would highly suggest any of Williams books if you are really interested in knowing more about turkeys and becoming a better turkey hunter. The art and science of the wild turkey is one of my favorites, it blends some great scientific and behavior information with some sounds hunting advice