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Any answer will be general in nature because every single gobbler is different. So from my experience Rios gobble earlier(while still dark) and more on the roost. Rios also are more concentrated on the roost I've seen 10 or more Rios roosted together which would be very rare for Easterns. Easterns are usually not as numerous as Rios so you'll likely have fewer Gobblers to deal with and fewer hens. The actual calling of the two is not much different same calls for each bird and depending on your experience. If you've hunted lightly pressured Rios in good populations and try to hunt hard pressured Easterns on public land there will be a sharp learning curve. If however you hunt well populated private land Easterns it may not be any harder. The Rios I've hunted had only a few options for roosting which made finding them easy Easterns don't normally have such defined roost areas unless you happen to be hunting farm land were roosting areas are limited. The only real answer is you have to find the birds get close to the roost and from there calling is not much different, I would say tone down the frequency and volume to start, and from there it's still turkey hunting. On the difficulty scale I'd say your going from easier to harder Rios to Easterns.
If your talking South East your more likely to be hunting Easterns or a hybrid rather than true Rios. Oklahomas Eastern population have been down in recent years. I hunted western and North Western public land for Rios. I did not find them at all difficult to locate. Water....that's it water find the creeks and the draws along creeks and you'll find the turkeys or your in an area without turkeys. Again once you've found the roost there still turkeys hunt accordingly.
I will be making my first attempt at calling Easterns this Spring. I have called to Rios for the past 25 years, and was wondering - what differences, if any, should I expect from an Eastern Tom? I appreciate any input, and Good Huntin' !!