HAYWARD, WI (KDAL) - The annual American Birkebeiner cross country ski race is set for Saturday morning but events celebrating their 40th year kicked off on Thursday.  A record field of 10 thousand skiers have registered for the birkie and associated races and the snow and trail conditions are looking excellent.  The big race on Saturday begins at 8 a-m in Cable and finishes on Main Street in Hayward.