How do bees survive the winter? Inside the winter cluster 🌨️

A summer colony of up to sixty thousand bees becomes a much smaller community by winter. The drones are driven out of the hive in autumn: they aren’t needed in winter and would only eat into the stores.

In late summer and autumn, special bees are raised: the winter bees. While summer workers live only a few weeks as adults, winter bees can live for more than five months in cold climates, and they carry the colony through to spring. You can read more in our piece on the life of a honey bee colony.

When the weather turns cold, the bees huddle tightly around the queen on the combs. They make heat by vibrating their flight muscles without moving their wings – as if shivering. The energy comes from the honey they gathered in summer.

According to a 2023 British study, without brood the looser core of the cluster warms up to about 18 °C, while the bees in the outer layer sit at around 10 °C – if they get much colder than that, they die. When the queen starts laying again at the end of winter, the bees keep the brood at around 35 °C.

The bees constantly swap places within the cluster. For a long time the outer layer was thought to act as an insulating blanket for the core; the same study suggests the opposite: the tightly packed outer bees actually conduct heat away, so the cluster is an emergency response to the cold.

Bees don’t relieve themselves inside the hive; they hold on for weeks. If the sun comes out on a milder winter day, they fly out briefly to do it outside – this is called a cleansing flight. It’s perfectly natural and a good sign for the beekeeper: the colony is alive and active.

Near an apiary, small yellowish spots may appear on snow, washing on the line or a parked car. Annoying, but harmless, and it only lasts a few days.

In winter the beekeeper doesn’t open the hives: every opening chills the cluster, and the colony has to burn more honey to warm back up. In autumn they check that there’s enough food and that the hives are in good order, fit a mouse guard to the entrance and make sure the spot is sheltered and quiet. In winter they lift the back of each hive to judge by its weight whether the stores are running low.

The most critical time is the end of winter: brood rearing starts, the colony eats more, but nothing is flowering yet. If it stays cold and windy for long, the bees can’t fly out. After the winter of 2021–2022, the Hungarian Beekeepers’ Association (OMME) said about 200,000 colonies had died in Hungary; its president said the exact causes weren’t known, but pointed to the cold, windy early spring. You can read about the beekeeper’s work through the year in our piece on the beekeeping year.

A few things that help, in your garden or neighbourhood: