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OUTSIDE WINTERING OF SINGLE BROOD CHAMBER HIVES
By John Pedersen, Gil Pedersen, and Ed Pedersen of Pedersen Apiaries

The escalating cost of package bees from the U.S.A. during the 1970s and early 1980s, plus the discovery of, first tracheal, and later varroa mites in the U.S. during the 1980s, led most Canadian beekeepers to become self-sufficient in bees.  Being self-sufficient means wintering your bees, making splits for replacement stock, and either raising your own queens, or buying from available sources.

We began experimenting with wintering in the early 1980s. Some beekeepers advocated wintering indoors in insulated rooms.  These facilities are kept completely dark and have ventilating fans that can force cool air into the room.  Others were adamant that outside wintering, using insulated packs, with four hives to a pack, was the route to go.  We decided to try some of each method; wintering some in an insulated building, and some in insulated packs outside.  Most of the hives which were wintered indoors were in single brood chambers, while the outside wintered were all in double brood configuration.  The survival percentage was similar for both types of wintering with a slight edge toward the outside wintered hives.  By the spring of 1987, the last year that bees were available from the U.S., we needed to purchase only 100 packages to maintain our roughly 500-hive operation.  The rest were from successfully wintered hives plus some splits make during the summer season.

There was an ongoing problem with the inside wintered bees in as much that when the outside air temperature rose above +5C for more than a couple of days, we did not have enough fan capacity to deep the room cool.  After the middle of March it was sometimes necessary to move these hives outside to prevent them from becoming too active in the building.  Those hives that were moved outside in early spring would suffer if we then encountered a cold spell.

For the fall of ’87 and ’88 we continued our practice of wintering the weaker hives inside and the strong two-story hives outside.  During the fall of 1988, in addition to the weaker double brood chamber hives that we normally wintered inside, a group of strong double-brood hives was selected for an indoor wintering trial.  With these stronger two-brood chamber hives counted, there were about 2/3 singles and 1/3 doubles wintered inside that year.  The reason for putting strong two-story hives inside was to see if indoor losses were a direct result of weaker hives, or whether it was the indoor wintering itself that was at fault.  The results of the spring of ’89 seemed to show that there was a higher loss for indoor wintered vs. outdoor given the same strength of hives.

Our hand, vis--vis wintering, was forced when a fire in the summer of ’89 destroyed our warehouse.  The insulated hot room where we normally wintered our hives was pressed into service for storage of supers.  The only usable solution to this problem was to winter everything outside.

But we were confronted with a dilemma – how were we to deal with hives that were in single brood chambers?  Until this time we had taken for granted the “conventional wisdom” which held that to winter successfully outside, the hives had to fill two brood chambers.  Our solution was double up the packs of singles.

Packs were made with singles on top of doubles and a few packs with singles on top of singles.  To wrap these singles over doubles, we made up narrow packs that went around the top hives and were tucked inside the regular doubles wrap.  The singles on top of singles were wrapped with a regular double pack.

Survival of over-wintered bees in the spring of 1990 was good – certainly not the over 20% loss that we experienced in the spring of ’89.  What was evident, when hives were checked early in the spring, was that in those packs where singles had been placed over other hives, it was the bottom hives of the pack that sustained the higher losses.  We theorized that heat from the lower hive leaked upward through the plywood cover separating the two hives.  To over come this, we make up some insulated covers to use in subsequent years.  These made a marked improvement in the survival of the lower hives in the pack.

During the winter of 1989-1990, when we first overwintered everything outside, we worried for fear that we would lose all of the singles.  As mentioned above, this did not happen.  This outcome encouraged us to try more singles for the winter of 1990-1991.  Some of these we left as single story packs.  The findings, when we unpacked the next spring, were that there was no significant difference in single story or double-story packs.  The overall loss that winter was about 11%, with both singles and doubles close to this figure.

We encountered losses during the spring of 1991 which in retrospect, we should have anticipated.  In order to facilitate the inspection of the bottom hives of a pack, we moved the top hives aside.  If the bottom hive was alive, then the top hive was moved to another pallet in he same yard.  Many of the bees drifted back to the original pack, seriously weakening these relocated hives.  We overcame the problem in succeeding years by moving the upper hives to another yard.  Incidentally, those hives that were moved were again wrapped so as to avoid a repeat of our experiences of earlier years where hives, moved out of indoor wintering, could not cope with cold weather.  Our policy is to keep winter wraps on all hives until mid May.

In as much as the economics favour single over two-story hives, all double brood chamber hives have been phased out.  We now confidently winter all of our bees in single brood chambers in outside packs.  The fall of 1993 was the first year in which only single story hives were wintered.  The decision to phase out all two brood chamber hives was reinforced by the experience of the winter of 1992-1993.  That year 542 singles and 66 doubles were packed.  Our overall loss for the winter was around 8%, but of the 66 doubles, 16 died (or close to 25%).

In the fall of 1993 we made two decisions about wintering.  One was wintering all hives in singles.  The other was to eliminate packs with hives on top of other hives.  All hives were put into single story packs.  Losses in the spring of ’94 were about 20%.  It was high compared to our experiences over the past several years, but when checking with other beekeepers, we found that they had similar losses.  So it would seem that the problem was with the winter, or with the bees before being packed, and not just the single-story wintering.

One wintering application, which we now employ on a regular basis, was discovered by accident.  The circumstances of the discovery involved the location of one of our winter yards.  It is situated on the south side of a shelterbelt, consisting of three closely spaced rows of deciduous trees. An open field to the north of this shelterbelt allows the wind to pick up snow and push it through the trees.  The resulting drifts covered most of the packs completely.  It was close to the end of March or later before the snow melted sufficiently for the bees to commence flying.  But despite this burial there, was only one dead hive in a yard of forty. When we evaluated the results of this experience we decided to deliberately shovel snow over some packs in other yards the following winter.  The results confirmed our previous conclusion, so we now make it a practice, as soon as there is enough snow, to visit all of our yards and completely cover the packs.  Our theory is that this method evens out the fluctuations in winter temperatures when it can be -40 C one week and up to + 10 C the next.  When the interior environment of the hive is evened out in this way, the bees are less prone to begin raising brood too early.

There are many benefits, economic and otherwise, to running only single brood chamber hives.  Some of these include:


There are also drawbacks to this method.  Factors that some might consider detrimental are as follows:


The tables shown here detail some of the highlights of wintering and honey production since 1988:

TABLE 1:  Colony wintering statistics:
 

Year
# Hives
Single
Double
Inside
Outside
Survival
%loss*
Nucs sold
1988
500
140
360
300
200
390
22
 -
1989
462
120
342
-
462
409
11.5
-
1990
508
240
268
-
508
454
10.6
-
1991
542
280
262
-
542
484
10.7
-
1992
608
542
66
-
608
559
8
-
1993
672
672
-
-
672
548
18.5
14
1994
740
740
-
-
740
N/A
N/A
36

 *Losses counted are those hives that are either dead or so weak that they must be united when pack is first inspected in the spring.  Some losses reported are hives that are not queen-right and so must be united with other hives.  These technically are not “winter losses”.

TABLE 2:  Honey production 1989 – 1994
 

Year
Producing Hives
Total Production in lbs.
Ave./hive
Saskatchewan Ave./hive 
Canadian Ave./Hive 
1989
425
44,200
104*
135
112
1990
460
67,160
146
160
133
1991
495
97,200
196
200
140
1992
550
103,400
188
210
133
1993
635
149,860
236
160
135
1994
640
204,850
320
200
144

*Honey production was adversely affected due to a fire on July 18 of this year.  The fire destroyed part of our warehouse, necessitating a period of clean-up, so there was a two-week hiatus before we were able to resume honey extraction.

Published in American Bee Journal, Volume 135, No. 5, May 1995, pp.324-325.
Published in Canadian Beekeeping, Volume 135, No. 5, May 1995, pp.152-153.

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