Alan asks about his hive that appeared very strong a month ago, and is not
virtually dead.  He suspects he left too much room for them to heat.
 
Alan, if you think about it I think you will agree that a month ago, when
the hive was strong, you had all ready been through the worst part of your
winter in Ann Arbor.  The bees survived those temperatures just fine, and
the amount of space in the hive had no effect on their ability to keep warm!
 
By suspending thermometers inside wintering hives, studies have shown that
the bees only keep their cluster warm; they do not attempt to keep the total
hive space warm.  Therefore you giving them a lot of honey and room did not
have an adverse effect.
 
Based on your description, the bees almost certainly died of excess moisture
inside the hives.  Now, "moisture" does not hurt.  However, the moisture
permits growth of other ugly things, principally bacteria and molds, and
these kill bees!  The moisture is caused because the bees eat all winter
long, and use the food to "shiver", creating heat, which warms the cluster.
This same heat causes condensation.  As a beekeeper one must allow this
moist heat to escape the hive.  Dry cold does not hurt bees, condensation
kills them!
 
There are many many ways of allowing the moist air to escape the over
wintering hive.  I will list some of them and make some comments:
- Drill a 1" auger hole above the hand hold on the top hive body.  This is
what I do.  The disadvantages are that you are putting a hole in your new
wood and as you move equipment around the hole may be where you don't want
it.
- Prop up the outer cover about 1/8" with stones, a piece of wood, etc.
This works fine, but you have to be certain that by doing this the cover
does not blow off during the winter.
- Cut a gap about 1/4" high and 1" wide in the outside of the inner cover.
This works fine, but if you don't do it to every inner cover you will
someday kill a hive because they did not have ventilation and you thought
they did.
- Put a 3/8"-1/2" piece of fiber board underneath the inner cover.  This
will absorb moisture and it will wick to the outside air.  I know a very
successful commercial beekeeper who does this with 2,000 hives.  The only
disadvantage is that the fiber board is another piece of equipment.
 
You did not mention whether you treated for tracheal mites by using grease
patties.  If you did not, your bees might have been weakened by these mites,
but the amount of moisture you described is almost certainly what killed
them.
 
Best of luck in 1999,
Lloyd
Lloyd Spear, Owner Ross Rounds(tm), the finest in comb honey production.
http://www.rossrounds.com