Checked my hive yesterday, almost cancelled as it was cold in the morning but warmed right up mid-afternoon.
Two/three weeks ago they had emptied a previously full super of honey (top box in brood + half), leaving 8 empty frames - yesterday these were crammed full of sealed brood, solid laying pattern with a tiny amount of stores in the top corners. Bottom box has total of around 3 full frames of BIAS, spread across the middle 5 frames, flanked by some honey stores and lots of pollen, although the outside frames are empty (I was expecting one to be, as I'd just replaced the frame feeder that was in there over winter).
They had built comb between the two sets of frames and started raising drone brood in it - some sealed. There is also a small amount of sealed drone brood in the bottom box.
So, I umm'ed and ahh'ed and then finally decided to add a QE and super, despite the cooler temperatures that are predicted, hoping they'll be OK in a double-walled hive with the top insulation still on. I took a peek through the glass crownboard just now and there are 20 or so bees up top, investigating their new space.
Will be checking again next week for queen cells - I have another complete hive that needs populating this year! Just starting my second year, so all very exciting
Nick