Honey Bees in the Garden: The Winter Cluster

By (@Mindy03) on
At the end of summer honey bees begin getting ready for winter survival. The drones are killed, either by stinging or they are herded out to perish in the cold, cruel world. Brood production stops when winter bees have been hatched to get the colony through winter, and honey stores are built up to feed them during the coming months.

Just as gardeners store their harvest to supply them with food during the winter, so do honey bees store nectar and pollen.  Let's take a closer look at what goes on in the hive when winter comes.

The bees that go through winter are not the same as the bees that you see in the spring and summer.  They have fatter bodies than summer bees; their bodies must hold more food to nourish them during the winter.

2011-10-27/Mindy03/7c5a73They live longer than summer bees; four to six months compared to six to eight weeks for summer bees. The sole purpose of the winter bees is to get the colony through to spring.

As long as the outside temperature remains above 64ºF the honey bees are dispersed throughout the hive but once the outside temperature drops below 54º-57ºF, they congregate together to form a cluster. At the beginning of winter the cluster is in the center of two hive boxes. It begins at the top bars of the frames in the lower hive box and covers and spreads beyond the bottom bars of the top hive box. As winter progresses the cluster moves upwards toward the top of the hive.

Honey bees generate heat by vibrating their flight muscles. Instead of activating their wings, the vibration causes the muscles to work against each other to produce heat; pretty much like we do when we shiver when we are cold.

The cluster consists of two layers of honey bees, the core and the mantel. The core bees maintain a temperature between 64º - 90ºF at the center of the cluster. The queen remains at the center of the core bees because it is important that she survives to build up the colony in the spring.  The mantel bees maintain a temperature between 48º - 57ºF and act as insulation for the core bees. The bees rotate through the mantel of the cluster to the core which helps them maintain a viable body temperature and lets all of the bees have access to the food stores.
If the mantel bees' thorax temperature falls below 48ºF they can not work their flight muscles and will go into a chill coma and fall off the cluster.

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Only the cluster is kept warm, the rest of the hive is the same temperature as the outside air. The metabolization of honey produces carbon dioxide gas and warm water vapor. Carbon dioxide is heavier than air and will settle to the bottom and flow out the bottom entrance.

The warm, moist air rises above the cluster and hits the cold inner cover which causes condensation. This cold condensation drips down on the cluster as ice cold water. The icy water will chill the bees and cause their death.  To prevent this the beekeeper should provide ventilation at the top of the hive so the water vapor can flow out.

 

Once the temperature drops enough to cause the bees to form their winter cluster, the only time they will venture outside is when the temperature is above 50ºF. They will take short cleansing flights during these times as they do not defecate inside their hive.  In subtropical climates the bees may not form a winter cluster at all.  They will continue to forage and raise their young all year long.

If winter is mild the bees will survive well but if the outside temperature remains too cold for too long the bees can’t move and will starve to death even though there may be plenty of food stores available.2011-12-07/Mindy03/22f311

The beekeeper can help the bees by making sure they have enough honey stores to get them through, providing windbreaks to block cold winter winds and ventilation at the top of the hive.   Beekeeping supply catalogs carry all kinds of products designed to help you winterize your hive from hive wraps to special inner covers.  One of the most important tasks a beekeeper in snowy regions has is to clean off the landing board in front of the entrance.  This aids in ventilation and allows the bees to go outside if the temperature warms enough before the snow melts completely.  

 

Additional source: The Backyard Beekeeper by Kim Flottum

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Comments and discussion:
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Good information by vic Jan 31, 2014 6:23 AM 22

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