i've kept bees in central mn since 1995 and winter my colonies over. 

i'd rather enter a bee yard in mid winter and see some dead bees on the ground in the snow then 
nothing.  nothing means deadouts, while some dead bees usually means healthy hives. 

those dead bees are probably from cleansing flights and has nothing to do with the published 
symptoms of CCD.  you may wish to visit the MAAREC web site and review the FAQ's concerning CCD

here is a web link to get you started

http://maarec.cas.psu.edu/FAQ/FAQCCD.pdf

a couple of hundred lost bees to cleansing flights per hive is nothing as new brood will be hatching 
in the next month or two. 

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