mbc
I know you're in the middle of the gulf stream but did you actually open up and go through brood frames to have a look?
It was 'christmas crackers' here all week!
richard
Yup. Split a few frames and had a peek down on a couple of the hives I deemed most likely to have brood = quick split with hivetool, shine torch and look, push frames back together, drizzle, close up and go, all in less than 2 minutes.
I'm not pretending that they wouldnt have been better off being left in peace, but curiosity got the better of me (and I also wanted to make an informed decision about whether to carry on oxalicking the others).