While I was adding a fresh new box to my hive, I noticed that there are two uncapped queen cells and a host of drone cells in one of the boxes. Assuming the colony is raising a new queen as part of the swarming process (as opposed to supersedure), is there any way in which I can estimate how many days until the swarm is likely to issue?
Would the colony wait for the new queen cells to be capped before they swarmed, or could they go at any time?
Graham, Reading Berkshire
Simple Bees 
I think the books say the swarm will leave when the first queen cell is capped but it then depends on the weather and the bees, so personally I assume that there will be a couple of weeks where I need to be vigilant if/when I see queen cells as I’ve done lots of calculations in the past and they have gone days before or after they “should” have! Sorry: that’s not a very helpful answer but I remember reading a book about bees and swarming where it said that swarming is more like giving birth than we give it credit for (ie doesn’t conform to a set timetable) so perhaps keep a close eye on your trees and hedges at your apiary and visit your hive(s) on a sunny day to see if they’ve swarmed. Mine nearly always go at lunchtime!