"Good point. I think historically, this refers to colonies that are below the strength needed to survive winter. The idea is it's easier and cheaper to ditch them at the end of the season and make new ones. "

What is a colony that does not have the strength needed to survive winter?  Last year I went into winter with a colony I expected to be dead by Christmas.  It had way more than enough honey but was only two frames of bees in October.  In NE Ohio after mid October you can count the forage days left on the fingers of one hand at best and that was sure true last year.  They did fly one day in mid November and were bringing pollen in from someplace.  That hive was still alive but very weak March 1 with only a palm sized patch of brood.  Then mid March we got a sudden cold spell with 10 below F zero temps and that killed the hive.  If not for that cold spell I think the hive would have made it to warm weather.  The strongest hive I had last summer only had two frames of bees on April 1.  It had lots of food and pollen stored.  The colony next to it went into winter the same strength and died in the March cold snap with lots of honey left.  Both had young
 queens.

I think there are a lot of factors in what allows a colony to survive winter.  Some mid 30 F days followed by a sudden drop to sub zero F is tough as the bees may not be able to recluster fast enough, particularly if the hive is weak.  Mite and disease loads are a factor.  Some weak hives in the fall are the result of mites and/or disease and those are not likely to make it.  Some weak hives may just have had some bad luck in the summer.  Lost the queen and did not get a new one until pretty late for a variety of reasons.  They just might make it.  Food is a factor although I have never lost a hive that was out of honey.  Food the bees can get to in cold weather is a factor.  I have seen dead hives that had plenty of food several frames from where the dead bees were.  

Dick

" Any discovery made by the human mind can be explained in its essentials to the curious learner."  Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists.   "For every complex problem there is a solution which is simple, neat and wrong."  H. L. Mencken

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