My first two years of graduate work have concentrated on the influence of protein availability on the ability of honey bees to overwinter.
Brood rearing ceases in colonies in late fall and the workers produced at this time are long-lived "winter" bees that cluster within the colony from late fall to spring. Winter bees are characterised by hypertrophied fat bodies and hypopharyngeal glands, which are two major locations of internal protein storage.
Aside from internal worker reserves, protein is also stored externally as pollen in the honey comb. Over the winter, bees utilise these resources to provide protein for the nutrition of developing larvae.
A colony must begin rearing young replacement bees in late winter in order to build colony strength for the spring, long before adequate pollen foraging conditions exist. When fall or spring pollen supply is limited, protein-starved colonies will have to compromise the quality and/or quantity of the workers that are produced for and by the overwintering population. Previous studies have demonstrated that protein status plays an important role in the ability of colonies to overwinter, but the influence of protein availability on the development of the overwintering population and the spring population that it produces remains poorly understood.
In my first field season, I examined the trade-offs made in the production of spring workers by overwintered colonies that were pollen-stressed (low pollen) or pollen-rich (high pollen) prior to spring foraging. I estimated both the quantity (area of sealed brood) and the quality (weight, size, asymmetry, total protein content, longevity and nursing behaviour) of workers reared by these colonies in the spring, as well as honey production in the following summer.
Colonies that had pollen supplements in early spring produced two to four times more brood than control and pollen restricted colonies, respectively, and only supplemented colonies reared brood in significant amounts before natural pollen foraging began.