The European honey bee, Apis mellifera, is unique among most insects because the colony remains active throughout the cold months instead of entering true dormancy. This continuous activity requires bees to constantly consume fuel to survive the winter. Survival depends on managing stored resources, primarily carbohydrates, to power the colony’s heat generation until new forage is available in spring. The colony’s nutritional needs shift over winter, moving from a simple carbohydrate requirement for warmth to a complex protein need for raising a new generation of workers.
The Honey Bee Winter Cluster
When temperatures inside the hive drop below approximately 57°F (14°C), worker bees form a dense, protective structure known as the winter cluster. This collective behavior is the colony’s mechanism for thermoregulation, allowing them to survive conditions that would instantly kill a single bee. The cluster consists of a tightly packed outer mantle and a looser core.
Bees within the core move freely, accessing food and caring for the queen, while the outer layer acts as insulation. To generate heat, bees vibrate their powerful flight muscles isometrically, flexing them without moving their wings. This muscle activity is a metabolic process requiring a continuous source of energy, making food consumption necessary throughout the cold period.
The core of a broodless cluster is maintained at temperatures around 68°F to 85°F (20°C to 29°C). This temperature increases dramatically once the queen begins laying eggs. When brood rearing starts, the cluster center must be kept at a stable 90°F to 95°F (32°C to 35°C) to ensure larvae develop correctly. The cluster’s size and density regulate this internal temperature, with consumed fuel directly powering the heat-generating muscle movement.
Stored Honey as the Primary Fuel
Stored honey is the sole carbohydrate source fueling the colony’s heat production during winter. Honey is stored nectar that bees have reduced in water content and enriched with enzymes, giving it a long shelf life. This high-sugar food provides the concentrated energy needed to power the constant muscle vibration required to maintain the cluster’s warmth.
Throughout the winter, the cluster must slowly move across the honeycombs to access fresh honey stores. If the weather remains too cold for extended periods, bees may be unable to break the tight cluster to reach honey just inches away, leading to starvation despite having reserves. The total amount of honey needed varies significantly by climate; a colony in a cold region may require 60 to 90 pounds of stored honey to survive the winter and early spring.
During the coldest months, the nutritional focus is almost exclusively on carbohydrates, as the colony often ceases brood rearing entirely. This minimizes the demand for protein, which is needed to feed developing young. Colony survival depends on the workers’ ability to metabolize honey efficiently to maintain the temperature gradient between the cold exterior and the warm core.
Using Pollen Reserves for Brood Rearing
While honey provides energy for warmth, stored pollen, known as “bee bread,” supplies protein, lipids, vitamins, and minerals. Pollen is not used for heat generation but becomes important when the colony prepares for spring. As daylight hours lengthen, typically in late winter or early spring, the queen begins to lay eggs again in anticipation of the foraging season.
The resulting larvae require a high-protein diet, provided by nurse bees who consume stored bee bread to produce a protein-rich secretion. This pollen is reserved to fuel the growth of the next generation of worker bees. Colonies entering winter with higher-quality pollen stores, often richer in amino acids and lipids, are better equipped to raise a robust first round of brood.
The initiation of brood rearing represents a significant nutritional shift and a sharp increase in the colony’s overall food consumption. The protein from the pollen reserves allows the nurse bees to develop their hypopharyngeal glands, which are essential for feeding the young. Without adequate protein reserves, the colony cannot successfully raise enough new workers to replace the older bees that die off naturally.
Beekeepers and Supplemental Nutrition
When a colony’s natural honey stores are insufficient, beekeepers often provide supplemental food to prevent starvation. Liquid sugar syrup, typically a concentrated mixture of two parts sugar to one part water, is common in the fall but generally avoided in deep winter. This is because cold temperatures can cause the syrup to chill the bees or ferment, and bees struggle to process liquids when clustered.
Instead, solid sugar feeds are used during the coldest periods because they do not introduce excess moisture into the hive. These supplements, which include candy boards, fondant, or dry granulated sugar, are placed directly above the cluster. These carbohydrate replacements are emergency rations used until the weather warms and the bees can access their perimeter honey stores or new nectar flows begin.
In late winter, beekeepers may also introduce protein patties, which are supplements made from pollen substitutes. These patties mimic the nutritional profile of bee bread and are used to stimulate and support early brood rearing. By providing this protein, beekeepers aim to accelerate the production of new workers, ensuring the colony is strong enough to capitalize on the first major nectar flow of spring.