I'm going to disagree with the previous replies - I don't think it is 'nothing to worry about' at all.
I used to have a similar amount of condensation in the oil filler cap on my old ZR. As here, people kept telling me it was "just condensation due to short runs in cold weather, and perfectly normal".......except that I wasn't doing short runs, and like you, my coolant level was dropping from max to min every few hundred miles. I was also getting residual pressure in the expansion tank when cold, and eventually started to see signs of emulsion in the coolant too. Head gasket was changed, and lo and behold, no more condensation in the oil filler cap.
Similarly, my current ZR (which had a failed head gasket when I bought it) has never had any condensation at all in the oil filler cap since the new head gasket was fitted (even in the winter) in spite of nowadays doing a lot of shortish runs and being parked outside overnight, (and the coolant level has never needed any topping up in 4 years and 25000 miles).
My opinion (for what it's worth) is that you have a slight seepage of coolant past the head gasket - not serious at present - I continued to run my old ZR with a similar coolant loss and condensation in the oil cap (as well as residual pressure in the expansion tank when cold indicating probably HGF at the fire rings) without serious problems developing for almost 2 years, before appearance of traces of emulsion in the expansion tank finally prompted a head gasket replacement.
The rate of coolant loss needs frequent monitoring and any sudden increase, or the appearance of traces of mayo in either the oil filler cap or the expansion tank should prompt more definitive checks for HGF and subsequent replacement.