It is October or perhaps November. You open your hives for a quick inspection only to find there is no brood. None! Not a single cell, capped or otherwise. You panic, wondering whether you should replace your queens (tricky this time of year), combine your colonies, or just give up. You blame mites, mite treatments, predators, diseases, bad weather, weak queens, and yourself.
So what is wrong with these colonies? My first guess is “absolutely nothing.” Your colonies have little or no brood because it’s that time of year. Here in the northern hemisphere, brood rearing slows dramatically or stops altogether as the weather begins to cool.
The winter brood nest
Beekeeping in Western Canada, a thorough all-purpose beekeeping book published by Alberta Agriculture and Rural Development, explains it like this (p.6):
As fall progresses, egg-laying by the queen generally ceases, and there is a period of from one to three months during winter when there is little or no brood rearing.
The ABC & XYZ of Bee Culture (p. 43) tells us that brood rearing begins anew after the winter solstice:
Brood rearing begins in mid-winter (end of December to January in temperate climates), accelerates in late winter and early spring, reaches a peak soon after the first forage becomes available, reduces later in the summer, and ceases entirely in autumn. (emphasis added)
Consider these two statements together and you can see that one to three months before the winter solstice puts you back in October. So basically, you may have no brood in the months of October, November, and December.
Variations due to temperature
The actual beginning of broodlessness will vary with local conditions, as will the length of time. Colonies further south where winter temperatures remain mild, may never be completely broodless. Still, even in the south, the amount of brood is lower in the winter.
My own observation is that the length of time (the one to three months) is not the same every year, but is dependent on local weather conditions. So maybe last year, for example, broodlessness started later. Maybe you didn’t notice it because your hives were already buttoned up for the winter. If broodlessness comes earlier in the year, you are more apt to notice it.
Advantages of a small or missing brood nest
All species evolve in ways that help them survive. A period of broodlessness may have a number of advantages:
- Some researchers have suggested that a broodless stretch allows the queen a period of rejuvenation. She gets to rest and build her strength before the next onslaught of egg-laying.
- The broodless period reduces the population of the hive by attrition. As bees die, fewer are left to feed. There is an optimum population level for any colony, one that is large enough to keep the colony warm but small enough that the food supply will last till spring. Colony size in winter varies, but it is highly dependent on sub-species. Carniolans, for example, overwinter with smaller colonies than Italians.
- A broodless period also conserves energy in another way. When no brood is present, the cluster is maintained at a temperature of around 20°C (68°F) in the center. Conversely, a cluster with brood is maintained at about 34°C (93°F). To sustain this higher temperature, the bees must eat a much greater amount of food. So as you can see, a long broodless period is a significant energy-saving strategy.
The Hive and the Honey Bee (2014, p. 89) sums it all up:
There is little or no brood rearing during the coldest part of the winter and colonies reach their lowest population size as winter progresses. However, in late winter the queen begins to lay and brood rearing commences. This requires that workers elevate the temperature to 34-35 degrees C inside the cluster around the brood.
Colony size is not static
Colony size and the amount of brood rearing is in a constant state of flux—nothing about a honey bee colony is static. I’ve written this many times before, but there is a simple rule of thumb to help you remember what is happening inside your hive. Just divide the year into two parts, the growing part and the shrinking part.
Basically a honey bee colony increases in population from the winter solstice to the summer solstice and decreases from the summer solstice to the winter solstice. Adult populations are highest just before the downturn (late June) and lowest just before the upturn (late December).
This schedule is not intuitive, especially to a new beekeeper, so it takes some thinking. The ABC & XYZ of Bee Culture states it like this:
The striking thing about this pattern is that it is so different from the pattern of when forage is available.
But when you think about it, a colony must build up before the major honey flow if the bees are to take advantage of it and store it for winter. Likewise, the colony needs to shrink before extreme cold sets in so food supplies are not rapidly consumed.
Think like a bee
When it comes to understanding your colony population dynamics, it helps to think like a bee. And a bee, it seems, is a good planner with the goal of protecting the future of the colony. My advice is to read a good book on bee biology and plot brood expansion and contraction on a calendar. You will then know what to expect before you open your hive.
Honey Bee Suite