I don't disagree with JBM's comments about the potentially deleterious effects of some recent husbandry practices (like reliance on fondant feeding). The way I look at it is that, all things being equal - and barring a catastrophic/irrecoverable event (like Queen loss) - EVERY colony which, in Autumn, is 1) well housed 2) strong/well balanced 3) well provisioned 4) disease free, and 5) having low varroa loads (i.e. having been treated successfully) will overwinter OK. Why wouldn't it ?
QED (assuming you subscribe to that blunt assessment), any abnormal losses will be normally be attributable to one of a) inadequate stores, b) disease (e.g. nosema) or c) varroa load
I don't think that's too much of a generalisation, and, when I have experienced losses (including one particularly bad year), I have usually been able to pinpoint the cause, which has either usually been i) nosema, or ii) bad beekeeping (weak colonies going into winter, ineffective treatment, underprovisioning).
Mostly, when I speak to other beekeepers (and I do speak regularly to very many members of our Association), I find that the tales I hear about winter losses are broadly in line with my own experiences. I guess that these might normally vary from the 10% to 25% levels depending on the year, and my guess would be that - in statistical terms, the standard deviation would be low (i.e. most people hovering around those averages).
So far, some of the chats I have had this winter with members (many very experienced) are quite alarming. It is not uncommon for me to hear of total apiary losses. That is completely at odds with my own current experience, where I have 12 colonies (7 hives/5 nucs) which all look to be faring well.
That's not me being smug or boastful, but just a way of explaining that I would not be surprised if we come to learn of higher than average reported losses this year, but possibly with a radically higher standard deviation. That is to say, some beekeepers in a locality experiencing low/normal losses, and others, inexplicably, being hammered.
Maybe twas ever thus. However, I would have to hope that the NBU alarm bells would ring loudly in that event, as the root cause would clearly need understanding, and there are potentially other correlations and inferences to be made from in the related survey data - e.g. treatment methods / timings, quite aside from field investigations.
I guess this is what the US agencies (assuming they have escaped the cull) are now doing to get to grips with the spike in "CCD" over there.
It would not surprise me at all to discover, for example, that those experiencing dramatic losses here are doing so due to varroosis caused (in spite of the beekeeper treating 'as usual') by resistance to Amitraz (e.g. Apivar) or to pyrethroids (like Apistan), with those closer to the average treating with e.g. organic acids.
Time will tell, I guess.
