Bees are one of the most important pollinators in the world, but they're also often misunderstood. Bees live in colonies, and each colony has a different life cycle.
Honeybees, bumblebees and solitary bees all have their own ingenious methods and techniques for surviving a chilly winter.
So how do bees survive a long winter without flowers or other plants to forage? Well, it's all about their hives and nests!
In the winter, managed honeybees kept by beekeepers reside in hives. Honeybees are social insects and live together in large colonies with a queen, normally a few hundred workers and a few hundred drones.
Wild honeybees live in nests typically located in tree trunks or any available natural cavity. Due to the added insulation provided by wild nests as opposed to wooden hives, it's rare that wild honeybees need to work as hard to keep the colony and most importantly the queen warm.
Honeybees in hives work together in winter to keep their hive or nest warm by shivering their flight muscles so that they can generate heat through muscle movement. Within the brood cluster, the worker bees cluster around the queen to transfer their body heat and keep her warm for the cold winter to come.
Both wild and managed colonies will start to produce an excess of honey towards the end of the summer season. This honey store will be used to sustain them over colder months when they are unable to take foraging flights for nectar and pollen.
All of these bees in a small enclosed space with little airflow create a concentration of carbon dioxide that would be deadly to humans but actually acts as an advantage for the bees as they overwinter. Interestingly this increase in carbon dioxide is observed to decrease rates of Varroa mite in the hive and acts as a natural way of removing harmful parasites from the colony.
This process of surrounding the queen to keep her warm is known as a thermo-regulating cluster.
It's clear that wild honeybees do employ these tactics in severe circumstances but this has become a norm for bees maintained by humans.
Unfortunately, all-male honeybees (drones) will die off as temperatures start to drop leaving just the queen and workers to survive the winter.
In warmer climates where winter temperatures don't fall below 10°C honeybees will continue to operate as normal, collecting nectar and pollen, reproducing, and swarming to find a new home when their numbers exceed the current hive or nest.
Check out this video from Scientific American that breaks down the process managed colonies go through over winter:
Bumblebees opt for a very different approach to winter than honeybees. Unlike their close relatives, bumblebees have an annual lifecycle which means that none of the bumblebees from early spring will live to see the next summer.
At the end of the summer season into autumn, bumblebee nests will begin to produce virgin queens. These queens will mate in mate with males of the species to ensure the survival of the species into the following summer.
As winter approaches the old queen, workers and males will all begin to die off leaving just the virgin queen to either begin a new nest or hibernate until the temperature rises enough for her to reemerge and seek out a suitable location for her new home.
Which of these two options a virgin queen will choose is entirely down to temperature. With rising global temperatures UK bumblebees have been observed forgoing hibernation due to the relatively mild winter.
This change in behaviour is even more likely if there is a selection of suitable winter flowering species in close proximity to the nest, offering a whole year-round buffet for local bumblebees.
In colder areas where bumblebees do choose to hibernate they look for shelter locations that provide insulation to keep them warm and protected from the elements.
Suitable nest locations include:
These nests are typically between 5cm and 15cm deep and can be at risk from enthusiastic gardeners starting early in the season.
With climate change playing havoc with our temperatures and in turn animals and insects you may occasionally see virgin queens taking flight during particularly hot winter weather despite it being far too early to emerge.
Here are some bumblebees that opt to brave the cold temperatures to go about their daily foraging.
Solitary bees are often overlooked but make up huge swathes of the bees we see in gardens all over the world. The term solitary bee covers a vast range of species with some of the better-known species being the ashy mining bee, carpenter bees, mason bees and Leafcutter bees.
The majority of solitary bees operate on an annual cycle much like their close relative the bumblebee. Bees that fall into this group use the summer to collect stores of nectar and pollen for their nest. Their nest will house eggs laid in summer ready to become the next generation the following summer.
When temperatures begin to decrease and they have ample food stores the females will actually seal the nest shut to protect the young inside from predators and the coming winter months. After this, both female and male solitary bees will die off in the colder temperatures.
Over winter the eggs hatch into larvae and consume the food stores gathered by the female bee the summer before. This gives them all the nutrition and sustenance they need to develop into young bees ready to repeat the process the following summer.
Now you have a much better understanding of the habits of bees over winter you can understand why it's so rare to see bees flying in the colder months.
It's going to be very interesting to see how the global increase in temperatures continues to affect bee behaviour and particularly their overwintering habits.
Check out some of our other short reads below to learn more about the fascinating world of bees, plants and pollinators.