Bees tightly gathered in a spherical shape during winter to keep brood and bee bodies warm, or during swarming to keep the bees that bivouac settled as a group (the swarm) until movement into a new homesite.
Bees cluster for two major reasons: (1) to stay warm enough and survive the coldest nights and overwintering period (winter cluster), and (2) to form the swarm bivouacbivouac:
a temporary cluster of swarming honey bees intermediate between leaving home and finding a new nest cavity
when they initially leave their home as part of colony reproduction.
Clustering inside the hive involves honey bees clustering over the brood area of the hive as a mechanism to maintain a high temperature for brood. Most of the year, the honey bee workers will be spread out over the frames going about their daily chores patrolling their beeswax comb. The brood area, however, must be kept warmer, around 92–97 °F (33-36 °C). The cluster area is the “heart of the hive.”
In winter, brood rearing is reduced or ceases. With the arrival of cool weather, bees cluster more tightly. They produce heat by moving their wing muscles. The inside of the cluster is kept warm, especially if there is brood present, and relatively open for bee movement. This area is enclosed by bees that gather to form a cluster shell. The temperature of bees forming the cluster shell will be lower, so they move inward to get warmer. Thus, as the temperature gets colder, the bees cluster even more tightly together.
When bitter cold weather arrives, the bees will not leave the cluster to bring honey close by. If the cold weather continues and the honey supply near the cluster is exhausted, the bees will die. This is especially a danger to small clusters. A honey bee colony can perish even when they have a full super of honey on top of the cluster position or if the stores are several frames away. The honey stores have to be in the right place for the winter clusterwinter cluster:
a closely packed colony of bees forming in winter to conserve heat
to access it.
Overwintered colonies may emerge as small colonies covering only one to three frames with the brood cluster. This may be due to poor adult population survival (perhaps by mite damage in the fall not enabling colony to rear sufficient numbers of fat fall bees), or to late establishment of the colony (because of nucnucleus:
also called a "nuc;" a smaller colony of bees usually with three to five frames. Nucs are splits (divides) made from larger colonies. Nucs are purchased as a method of starting a new colony or as a resource to use to bolster weaker colonies. See more information about nucs <a href="index.cfm?pageID=3093#standard">here</a> and <a href="index.cfm?pageID=3417#nuc">here</a>.
or swarm capture), or to lack of adequate honey stores. Disease (such as Nosema), pesticide-poisoning-caused loss of adults later in the season, or starvation in spring, likewise could be the reason for a small cluster in spring. Parasitic mite syndrome is also a possible reason for a small spring cluster. Yet another possibility for a small cluster is a cool, wet spring that delays normal colony development or expansion. A poorly mated queen might be the reason, too.
It is important to make a diagnosis and then stimulate the colony with sugar syrup or via addition of brood frames from other (stronger) colonies. An alternative is to uniteunite:
combine one colony with another; opposite of divide
a weak (small cluster) colony to a stronger unit by building a stronger colony. It may then be possible to split (divide) the colony to "replace" the loss of the small cluster colony.
thermoregulation, swarming bivouac (cluster)
PerfectBee. N.d. Fat Bees and the Winter Cluster. PerfectBee. Accessed 2023. https://www.perfectbee.com/learn-about-bees/the-life-of-bees/fat-bees-and-the-winter-cluster
“What a Healthy Winter Cluster looks like!”. YouTube, uploaded by Kamon Reynolds – Tennessee’s Bees, 13 December 2020. https://www.youtube.com/watch?v=ihLM2H2EgnY
Mangum W. 2016. Winter clusters seen with colors of heat. American Bee Journal 156(10): 1133-1135. https://bluetoad.com/publication/?i=336267&p=69&view=issueViewer and https://bluetoad.com/publication/?m=5417&i=336267&view=articleBrowser&article_id=2580346&ver=html5
Greenwood, D. 2023. At what temperature do bees cluster?. BeehiveHero. Accessed 2023. https://beehivehero.com/at-what-temperature-do-bees-cluster/
