Are bumblebees active during the winter?

Since the 1990s, naturalists have noticed that rather than hibernating, some bumblebees stay active over winter. These have almost all been identified as Buff-tailed bumblebees (Bombus terrestris) and it’s clear that a proportion of the queens produced over the summer have begun to establish nests in the autumn instead of going into hibernation.

The Trust is working closely with the national recording body, Bees, Wasps and Ants Recording Society (BWARS), to understand more about this behaviour – which species are involved, what’s driving the change, and how are they managing it?

You can help!

If you see a bumblebee between 1 November and 1 March, please record it at iRecord. Include as much detail as you can to help us answer these questions:

• Which species is it? The Buff-tailed bumblebee is by far the most common winter active bumblebee, but there are winter records of several other species too, though these may just be early-emerging queens.
• Which castes are involved? Queens, workers and males all tell us different things about the stage of the colony that they have come from.
• Where are these winter active bumblebees in Britain?
• Are the bees collecting pollen from the flowers or just feeding on nectar (or both)?
• Which type of flowers are being visited?
• What are the best winter weather conditions for winter active bumblebees?

Here’s what we know about winter active bumblebees so far

Hibernating queen bumblebees usually emerge in the spring (roughly March-May depending on species and weather conditions) and establish a nest. As summer fades to autumn, the old queen and all the workers and males die off, while the new queens enter hibernation. From October to March our gardens and parks are quiet. However, in recent decades this has not always been the case.

Starting in the 1990s, several species of bumblebee have been recorded through the winter months. Many records have been of queens in February, and these are likely to have just emerged early from hibernation. However, for the Buff-tailed bumblebee, queens and workers have been seen flying from October right through to March, collecting pollen as well as nectar, and males (and mating pairs) have been seen in early spring. Occasionally, the nests themselves have been found.

Winter active nests are able to survive due to the increasing amount of flowers which are available through the winter. Favourites include both non-native garden plants, such as Mahonia and winter honeysuckle, and native plants, such as White Dead-nettle, which can sometimes flower in winter.

Many of the sightings are in towns and cities. This may be because these areas tend to remain warmer, due to buildings and traffic, than the surrounding countryside. There may also be more winter flowering plants in towns, as plants like Mahonia are commonly used in street planting schemes and gardens. It may also just be that there are more people in towns so there are more eyes to spot bumblebees! There are still some sightings from the wider countryside, especially along the coast in the south and south-west of England.

Winter-active bumblebees have been recorded as far north as Dundee so wherever you are there’s a chance of seeing a winter-active bumblebee – please do send in any sightings to iRecord.