Lot's can happen between now and May, so I wouldn't be too worried at the moment. Both previous comments are good. Spring breeding locations may be entirely different from where turkeys reside the rest of the year, so they may be moving to more favorable habitat for that.
And just because they may have moved off of your property does not necessarily mean you can't keep track of them or other flocks in the area. Most places have public road systems that allow listening for gobbling activity (which is common once the breeding season gets into full swing), and there is no reason a guy can't use those public roads to get a feel for where turkeys are relative to where you may be able to hunt, even if they are not necessarily on your property.
