A colony needs two kinds of food, and they are not interchangeable.

Carbohydrate

Nectar supplies the energy for flight, for heating and for the winter stores. Where it is lacking, sugar syrup is given.

Honeydew is a second carbohydrate source, but unsuitable as winter stores: its high ash content burdens the gut of the winter bees.

Protein

Pollen supplies protein, fat and minerals. Without pollen no brood can be reared — not even with honey in the hive.

This is the commonest hidden limitation in spring: the stores look adequate and the colony still fails to build up.

Why variety matters

The amino acid composition of pollen varies by plant species. One source gives an incomplete protein package.

A colony with varied pollen is more resilient: immunity works better and the winter bees live longer.

That is why a colony in monoculture weakens even when it appears abundantly fed.

The fat body

What lets a winter bee live for months is her fat body, built from protein in late summer.

Pollen shortage in that period means weak winter bees — and Varroa damages precisely that tissue. The two converge there.

Water

Not a nutrient but a necessity: for cooling, for diluting crystallised stores and for making larval food.

Consumption rises sharply in heat and in early spring.

Minerals

Bees obtain minerals from pollen and from water. A water source that is not entirely pure — carrying some soil or plant matter — is often preferred over clean tap water.

The practical line

Improving the forage does more for nutrition than any supplement, and it supports wild pollinators at the same time.