I've noticed something similiar with my bees, they ignore syrup this time of year that I open feed even if it's warmed up, but they go nuts for dry pollen substitute that I have put out and water that I keep filled in an inverted 5 gallon bucket on the days when it gets above 50 degrees.I know it supposed to be a negative thing to give them pollen this time of year so I don't make a habit of it , but I figure the water would be ok if they don't get it there they will get the rank water from the ditch.