Keeping a small colony fed over the winter, either with dry sugar, fondant or a candy board, presents fewer challenges than keeping it from getting too cold.  When outdoor temperatures drop to about 55°F, honey bees begin to cluster, maintaining the center of their cluster between 85 and 96 degrees, depending on whether or not brood-rearing has commenced.  The thermal mass of a natural tree cavity provides much more protection from temperature extremes than the ¾” material of a standard Langstroth hive body.  Even the traditional 1” thickness of Abbé Warré’s hive bodies can’t compete with the typical 2-4” commonly found insulating colonies in natural tree cavities.  A generous cluster size therefore becomes especially critical in successful overwintering.  While some of my small, late-season colonies are in standard deep brood boxes, a few are housed in single westerns.  These tiny, single-box colonies have little chance of maintaining their cluster temperature in such an exposed configuration.  A past experiment stacking single western colonies atop full-sized colonies proved useful.  In this configuration, the heat rising from the full-sized colony helps to warm the smaller colonies, the bulk of the equipment and stores below serving to further buffer cold temperatures.

This oddball arrangement requires a few pieces of extra equipment.  Firstly, stacking the colonies means they need a way to be in close proximity without the bees to mixing or even touching one another.  This is achieved simply by installing a ¾” wooden shim with metal window-screen stapled to both sides.  This double screen prevents the fighting and trophylaxis that would occur with a single screen shim and allows the two colonies to maintain distinct populations.  Secondly, a separate entrance must also be provided for the upper colony (or colonies), which because of the impervious double screen, cannot access the lower entrance.  This can be done quickly by drilling a hole in the piggy-backed hive body (best done prior to bee inhabitation!), installing an inner cover with an opening cut in the rim, or in the case of a few of my colonies, removing the front screen covering the hole of the ventilation box.

Tar paper pulled back to show equipment. From bottom to top: screened bottom board with mouse guard; full-sized colony in deep and two westerns; double screened shim and inner cover; single western colony; modified inner cover with entrance, supplemental dry sugar and double screened shim above; second single western colony; modified inner cover with entrance; ventilation box with candy board; telescoping top.

One other accommodation I make for colonies stacked in this way is to provide wind and rain protection.  A colony that has been left to its own devices will carefully propolize any drafty or leaky spots in their hive.  I’ve found that making late-season equipment adjustments, especially those that limit the bees’ access to gaps, requires a little extra attention.  For example, changing out an inner cover to allow an upper entrance introduces a new piece of equipment that the bees have not had the opportunity to propolize.  The first driving rain or dip into the teens will compromise their ability to keep themselves dry and warm.  A simple way to compensate for these beekeeper-induced gaps is to cloak the unprotected joins with a wrap.  I use tar paper; it is inexpensive, dark (to absorb solar energy on cold, clear days), and because of its stiffness, relatively breathable.  In protecting unpropolized equipment gaps, it’s important to take care not to compromise air circulation.  Blocking air flow through the hive in our region’s cool, wet winters results in condensation dripping onto the cluster, a potentially deadly situation.

Tar paper wrap stapled, leaving openings for upper colony entrances and ventilation.

This weekend’s sun brought out a reassuring number of bees from all three compartments of my honey bee high-rise.  After a few gloriously warm hours of cleansing flights, they retreated back to their warm, dry homes as the sun dipped back behind the ridge.  With any luck, all three will survive to become productive, stand-alone colonies in the spring.