What Mr. Harrison said.  But, don't panic if it takes a while.  I recently removed the shims and top entrances from my hives, having left them on later into the spring than I normally do, and it took a good week before all the bees either figured it out, or else gradually died off (of old age, not from moving the entrance).  The first day was pretty chaotic, although some hives as a 'group mind' figured it out quicker than others.  It got progressively better each day.  The first night about a dozen bees clustered at the old entrance of one hive overnight, where they must have been cold and miserable (at least as much as a bee brain can experience 'miserable').  They were too cold and hungry to move, even by the next afternoon, and I moved them with a small stick, one by one, down to the entrance, where they promptly crawled inside.  They did not reappear at the old entrance.  I don't normally 'nurse' individual bees (and probably looked pretty foolish doing it), and can imagine the commercial guys shaking their heads as they read this post.  But, I felt bad for these girls, since they ended up suffering directly as a result of something I did.

Bill
Claremont, NH
My weather station:
http://www.wunderground.com/cgi-bin/findweather/getForecast?query=03743&MR=1

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