You'll occasionally see them strut any time of year. But for serious action you want to start looking around the second week in April through about mid May.
For the first time ever, KS has an archery only season starting April 1st. This means turkey hunters can be in the field 10 days earlier than usual. I'm interested to see how broken up the birds are then. In the past they've still been pretty bunched up even when the traditional shotgun season starts... We'll just have to see. I'm certainly excited about the expanded options.