Most bumblebee queens hibernate during the winter however towards the end of the 1990's a few winter sightings of Buff-tailed bumblebees (Bombus terrestris) workers were recorded. Winter colonies had previously been known from New Zealand where the species had been imported.
The buff-tailed bumblebee is our most common species but even so winter activity is only known at a few locations in the UK. From the distribution of records the availability of winter flowering plants seems as important as climate if not more so - none have been recorded further north than Hull*.
With few sightings there is still much to be discovered about these winter colonies. For example it is not known how many colonies that produce workers in December and January successfully complete their life cycle - see earlier post, Missing male bumblebees - a mystery?
Although I have been observing Buff-tailed bumblebees in Falmouth for the last three winters the odds of finding a nest were slim. In the end it turned out to a mixture of luck meeting a prepared mind. I sort of stumbled upon it but knew immediately what I had found.
How rare a find is it? To my knowledge the earliest winter nest (December through to February) was discovered in London last December and that is still active to date**. Brigit Strawbridge observed new queens carry pollen back to their old nest in late November 2011 but no males were seen. This was a very late nest to be active, not typical behaviour and possibly a second generation brood. See my post, Bumblebees - A Winter's Tale for more information on second generations. There is also the possibility that the new queens may have founded nests themselves rather than hibernate.
There is still much to learn about this winter activity and it is possibly variable from location to location and year to year. People continue to see winter active workers such as Philip Strange, who has seen them in Paignton for the second winter running.***
Even though the video above is an edited highlights of arrivals and departures it is clear this nest has been established for some time. How long would be a guess but possibly it might be the nest of the workers I began observing in December.
In the video you can see the bees are bringing back different coloured pollen this shows that they are visiting different species of flowers. From the data I collected while filming and intend to collect on my next visit it should be possible to estimate of the size of the colony.
It will be interesting to see how long the colony remains active, current thoughts are that it will reach its end soon but I am keeping an open mind. Towards its end new queens are produced and as they often return to the nest they will hopefully be easier to observe. Males unfortunately leave never to return, indeed recent research suggests they do not remember the location of their nest. I am going to need a bit more luck to spot them.
* See BWARS 2010 infosheet here Click
** Literally a hour after posting the blog I read that the colony was still active (there had been no news of it since December) and have revised this post.
***Read Philip's blog for details of the winter active bumblebees in Paignton. Click Here