The question is: as it is likely to be very cold for the next few days should we endeavour to feed the bees with sugar syrup so they survive the cold snap? I am tempted to do this but am concerned that opening the box even for a short time may do more harm than good by exposing the bees to the outside elements.
My Answer: weather is going to be cloudy with showers over the next 2-3 days and only 13 degrees today but the bees will fly at least some of the day. Mine are already out at 8.30 although the temperature is only about 10 degrees. I'm reasonably sure they won't starve.
Sounds as though you handled the swarm very effectively, well done.
I personally wouldn't feed them, mainly because I feel that it is "unnecessary fussing" with them. I'm sure you could make a good argument that it will get them started building comb more quickly, but swarms are incredibly motivated and they will be out there foraging strongly.
If you do open them up, you should minimise the time they are open while it is less than 15. So you would want to have everything ready for a quick lid off, insert feeder, lid on. Given that they are in a brood box with an empty super on top you could probably put in an inverted paint can feeder on top of the frames without too much disturbance - but they may all be hanging off the lid and the branch so it could get tricky!
Whatever you decide, you should go in and remove the branches and probably the super too fairly soon as they will start building wild comb very quickly - there is probably 5 cm already. So Monday preferably when it is going to be 18, but Sunday (15) if you need to be at work.
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