Zumer eluded to the problem; its spooking the birds that makes them associate a bad experience with the calling.
Turkeys hear other turkeys calling all day long, they hear other turkeys making soft sounds, loud sounds, alarming sounds, mating sounds, etc. And I do not believe turkeys have the cognitive ability to listen to a string of yelps coming from another ridge top and discern that the origin isn't a turkey, but a predator that has itself learned to accurately mimic its own vocalizations as a form of deception.
I am also not saying that preseason calling is OK, because birds will react to any kind of new pressure in their home ranges. Yet I always arrive at the following conclusion when I read these threads...
In Pennsylvania, we have a couple hundred thousand spring hunters, many of which hit the public ground we are fortunate enough to have here in PA. I wrote last year to a forum member here about opening day last spring as "valet parking at the state forest gates," and "other gates it was take a number and wait your turn to walk out the ridge top."
That kind of pressure affects the birds in a major way; all those hunters yawking on every calling device in their vests, much of that calling too loud and out of context. All those hunters pushing the birds around from one hollow to the next, bumping them off the roost, etc. Birds move off and then settle again, because birds are bumped by all sorts of predators all year long, and have learned to quickly settle down and get back to going about their day.
Yet the very next morning after the opening day onslaught of "calling" and bmping, gobblers are sitting on their roost branches at dawn gobbling their heads off, flying down and going to hens calling nearby. If preseason calling was as detrimental as some claim it to be, not a bird would be successfully called up on the second day of Pennsylvania's season and harvested. Conversely, I have had turkeys gobble at my call within a few hundred yards of the most crowded gates on our public ground, where three or four trucks are already parked.
The most dramatic form of "preseason calling" actually happens on opening day, call it "season calling," if you will. It takes the minor pressure of a truck stopping along a pull-off, a guy getting out and hitting a box call to an entirely different level of roost bumping, spooking on the ground, flushing off ridges, etc. Yet birds are still respond to calling the very next day -- sometimes within a few minutes of the flushing event. How often do we hear of stories of guys calling a gobbler, shooting and missing, and calling that bird right back in. Or breakig up a flock in the fall with a gun blast, waiting ten minutes and calling the flock right back to the bust site.
Back to Zumer's point, if a guy sits in the weeks leading up to the opener sitting in the woods, calling up gobblers and then causing them to spook, a turkey does have the ability to learn from that unpleasant experience. But to state as a conclusion preseason calling is some kind of irreverislbe, damaging act that should be avoided at all costs, well I dont think turkey behavior bears that to be fact. If they were that paranoid after a single experience, no two turkeys would ever trust each other enought ot be successful at getting together and reproducing.
