turkeys were hunted/habit altered to near extinction in ks. they were reintroduced in the 50s and have done really well. the increase in woodland habitat that emo talks about definitely helped, but a lot of that woodland habitat had already succeeded by 30 years ago, the turkeys just hadn't completed their occupation of it yet.
sys, study after study links loss (change) of habitat as the #1 reason bobwhite quail numbers have declined so much since the 60's. It just so happens this change (usually) also benefits turkeys. I can tell you without a doubt the areas I ran around in as a little boy are much different today. I recall seeing two turkeys in my life before 1997, and now if you drive this road in the winter time you might see 100 birds. I'll see if I can dig up some old satellite imagery.
(On another anecdotal note, about 7 years ago I went to a field trial for hunting dogs and the old timers were lamenting how they now have to release quail to run birds on, that just 10 years prior they were running exclusively on wild birds. They noted how the hardwoods had matured and there was no edge cover for the quail anymore.)
Anyway, one larger point I wanted to make, you'll hear a lot of bird hunters saying turkeys eat quail eggs or quail chicks, and they have wiped out the quail and such, and that just isn't true. It's the change in habitat, and not just smaller trees growing up to be big trees, but also farmers ripping out tree rows that once separated two fields to make one bigger easier to farm field.
On a related note, I am impressively unbelievably bad at hunting turkeys.