Another theory being explored is that the bees may be hybridising with foreign bees, which remain active in winter. It is thought that these may have escaped into the wild after being imported into Britain to help with the pollination of crops in poly tunnels.
The "winter bees" seem to be an entirely urban or suburban phenomenon. It appears that the queen bee only goes into a mini hibernation in October and then starts foraging again, rather than sleeping through the winter and waking up in March. However this could leave these bees